Hydronephrosis: what it means and how it is treated

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Finding out that a kidney is swollen on a scan can be worrying. The word hydronephrosis sounds like a diagnosis, but it describes an appearance: urine is collecting and stretching the drainage system of one or both kidneys. It is a sign that needs to be understood in context. It does not, by itself, tell us why it has happened, whether a cancer is present, or whether an operation is needed.

Many causes are treatable, and some cases can be monitored safely. The right approach depends on the cause, the degree and duration of blockage, kidney function, symptoms, overall health and, when cancer is involved, what matters most to the person receiving care.

What are unilateral and bilateral hydronephrosis?

Each kidney drains urine through a tube called a ureter into the bladder. Unilateral hydronephrosis affects one kidney; bilateral hydronephrosis affects both. A blockage may be within the kidney or ureter, or lower down where it affects the bladder outlet. A full bladder or difficulty emptying can sometimes cause dilation on both sides.

One healthy kidney can often maintain overall kidney function when the other side is obstructed. This can mean that a person with a one-sided blockage has few symptoms and normal blood tests. With obstruction affecting both kidneys, or a person who has only one functioning kidney, kidney function can become impaired more quickly. The scan appearance alone does not show how well each kidney is working.

What can cause hydronephrosis?

Causes may be benign (non-cancerous) or malignant (related to cancer). They include:

  • Kidney or ureteric stones, which may block urine flow and cause pain, blood in the urine or infection.
  • Narrowing or scarring of the ureter (a stricture), sometimes following previous surgery, instrumentation, infection or radiation treatment.
  • Bladder outlet obstruction or poor bladder emptying, including from an enlarged prostate before prostate surgery, urethral narrowing, a tight bladder-neck/anastomotic scar after surgery, or a bladder that does not contract effectively.
  • Anatomical or functional conditions, such as a narrowing where the kidney joins the ureter (a pelvi-ureteric junction obstruction), reflux of urine towards the kidney, or in some circumstance, pregnancy.
  • Blood clots or inflammation, which can temporarily obstruct drainage.
  • Cancer, either growing in the urinary tract or pressing on a ureter from nearby tissues or lymph nodes. Possible cancers include prostate, bladder, bowel, gynaecological and other pelvic or abdominal cancers. A cancer-related cause is only one possibility; imaging and clinical assessment are needed to establish the cause.

Prostate cancer and hydronephrosis

Prostate cancer can affect urine drainage in different ways. A locally advanced tumour may involve the bladder outlet or the area where the ureters enter the bladder. Cancer in pelvic or abdominal lymph nodes can press on one or both ureters. These problems are more likely with locally advanced or recurrent disease than with an early cancer confined to the prostate, but each person’s situation is different.

Hydronephrosis in someone who has had prostate cancer does not automatically mean the cancer has returned. Stones, infection, scarring, bladder-emptying problems and unrelated conditions remain possible. The team will consider the person’s history, prostate-specific antigen (PSA) trend, symptoms, blood and urine tests, and the pattern seen on imaging. Further tests may be appropriate if the cause is not clear.

After radical prostatectomy

After prostate removal, the bladder is joined to the urethra. Scarring at this join (a vesicourethral anastomotic stenosis, sometimes called a bladder-neck contracture) can make it difficult to empty the bladder. Significant retention may raise pressure in the bladder and contribute to dilation of both upper urinary tracts. A ureteric injury or later narrowing is a less common possibility. Recurrent cancer or enlarged lymph nodes can also obstruct a ureter, but this is not the only explanation.

Assessment may include checking bladder emptying, kidney function and imaging, with a camera examination or contrast study if needed. Treatment is directed at the level and cause of the blockage: for example, bladder drainage, treatment of a narrowing, or drainage of an obstructed ureter.

After salvage radiation therapy

Radiation can cause inflammation and, less commonly, delayed scarring in urinary tissues. Narrowing of the urethra or bladder outlet can interfere with emptying. A ureteric stricture after pelvic radiation is uncommon, but may develop months or years later. Salvage radiation after prostatectomy is generally directed to the prostate bed; hydronephrosis that appears afterwards still needs a proper assessment rather than being assumed to be a radiation effect or a cancer recurrence.

If imaging shows a narrowed ureter, the team may use CT or MRI, a contrast study, or a functional kidney scan to clarify its site, length and effect on kidney drainage. Treatment can be more complex in previously irradiated tissue, so decisions are individualised and may involve a reconstructive urologist, radiation oncologist, medical oncologist or interventional radiologist.

Symptoms and when to seek urgent care

Hydronephrosis can cause no noticeable symptoms, particularly when it develops gradually or affects one kidney. When symptoms occur, they may include pain in the side, back or abdomen; nausea or vomiting; blood in the urine; difficulty passing urine; or repeated urinary infections.

Please seek urgent medical assessment for fever or shaking chills with suspected urinary blockage, severe or worsening pain, repeated vomiting, very little or no urine, confusion, or feeling suddenly very unwell. Infection behind a blockage can become serious and may need urgent antibiotics and drainage. Sudden inability to pass urine also needs prompt care.

How is it investigated?

The first aim is to understand whether there is a blockage that needs prompt relief and what is causing it. Assessment commonly includes:

  1. A conversation and examination, including previous cancer treatments, operations, stones, infections, urinary symptoms and medicines.
  2. Blood tests, especially creatinine and estimated kidney function, and urine tests for infection or blood.
  3. Ultrasound, which can show dilation of the kidneys and bladder and whether the bladder empties.
  4. CT or MRI, selected according to the suspected cause and the person’s kidney function, to look for stones, strictures, masses or enlarged lymph nodes.
  5. Additional tests where useful: a MAG3 renal scan can assess each kidney’s contribution and drainage; cystoscopy or contrast X-rays can clarify the bladder outlet or ureter.

Not everyone needs every test. The clinician will choose investigations that answer the question while taking account of kidney function, previous treatment and the person’s circumstances.

Management options

Treatment is tailored to the cause and the degree of risk. The goals may be to protect kidney function, treat infection or pain, restore urine flow, enable other cancer treatment, or support comfort and quality of life.

Observation and treatment of the cause

Mild, stable hydronephrosis may sometimes be monitored with repeat blood tests and imaging, particularly if there is no infection, troublesome pain or evidence of kidney function decline. A stone may pass or be treated with medication, ureteroscopy or another stone procedure. Infection is treated with antibiotics. Retention may be relieved with a bladder catheter while the cause is assessed. A benign narrowing may be treated by endoscopic incision or dilation, reconstruction, or another procedure depending on its location and the person’s health.

Draining the kidney

If drainage is needed, there are two common approaches:

  • Ureteric stent (often called a JJ stent): a thin internal tube placed between the kidney and bladder, usually using a camera. It can avoid an external collection bag, but may cause urinary frequency, urgency, discomfort, blood in the urine or infection, and it usually needs planned replacement or removal. A tight narrowing or external cancer pressure can make stent placement difficult or less reliable.
  • Percutaneous nephrostomy: a small tube placed through the skin of the back into the kidney, usually by an interventional radiologist, to drain urine into an external bag. It can be useful when a stent cannot be placed, has not drained adequately, or rapid reliable drainage is needed. The tube needs care and periodic changes and can affect daily activities.

The choice depends on the site and cause of obstruction, infection, anatomy, kidney function, expected duration, other treatment plans and personal preference. Sometimes a nephrostomy is used first, with an internal stent considered later. Drainage can relieve pressure and help kidney function, but it does not remove the underlying cause; further treatment or monitoring is often needed.

When might palliative care be part of the plan?

“Palliative” can sound frightening, but palliative care is focused on comfort, symptom relief, support and quality of life. It can be provided alongside active cancer treatment. It does not mean that someone is being abandoned or that all treatment has stopped.

When hydronephrosis is caused by advanced cancer, a stent or nephrostomy may help with pain, infection, kidney function, or the ability to receive cancer treatment. It can also bring burdens such as procedures, hospital visits, tube or stent symptoms, repeat exchanges and complications. In some situations, drainage may not improve symptoms or kidney function enough to outweigh those burdens. Evidence in this area is limited, and outcomes vary widely; population averages cannot predict an individual person’s future.

There is no single point at which palliation is “required.” The decision is made with the patient, their chosen supports and the treating team. It can help to discuss:

  • What problem are we hoping drainage will improve?
  • How likely is it to help, and how soon might we know?
  • What would living with a stent or nephrostomy involve?
  • Could the result allow another treatment that matters to me?
  • What might happen if we monitor or manage symptoms without drainage?
  • What matters most to me now: time at home, symptom relief, kidney function, further cancer treatment, or avoiding procedures?

Choosing not to have a procedure is also a valid choice when it best fits a person’s wishes and clinical circumstances. The team can still treat pain, nausea, infection and other symptoms, and provide practical and emotional support. These conversations are best held early and revisited as circumstances change.

In summary

Hydronephrosis means that urine is collecting in one or both kidneys, but it does not identify the cause on its own. Many causes are benign and treatable. Prostate cancer, previous prostate surgery and radiation can be relevant, but a careful assessment is needed before drawing conclusions. Some people need urgent drainage; others can be monitored or treated in a less invasive way. When cancer is advanced, decisions about drainage and palliative care should be compassionate, individualised and guided by what is most important to the person.

References and further reading

  1. National Kidney Foundation. Hydronephrosis. Updated 2023.
  2. Mayo Clinic. Hydronephrosis: Diagnosis and treatment. Updated 2024.
  3. European Association of Urology. EAU Guidelines on Urolithiasis. See section on sepsis and anuria in an obstructed kidney.
  4. National Institute for Health and Care Excellence. Prostate cancer: diagnosis and management (NG131). Includes recommendations on upper urinary tract decompression for obstructive uropathy secondary to hormone-relapsed prostate cancer.
  5. Chorbińska J, Krajewski W, Zdrojowy R. Urological complications after radiation therapy—nothing ventured, nothing gained: a narrative review. Transl Androl Urol. 2021;10(8):3553–3566. doi:10.21037/tau-20-1217.
  6. Carilli M, et al. Management of ureteral stricture disease after radiation therapy for pelvic malignancies. Cancers (Basel). 2024;16(21):3561. doi:10.3390/cancers16213561.
  7. Shah M, et al. Malignant upper urinary tract obstruction in cancer patients: a systematic review. BJUI Compass. 2024;5(11):915–925. doi:10.1002/bco2.340.
  8. Gauhar V, et al. Nephrostomy tube versus double J ureteral stent in patients with malignant ureteric obstruction: a systematic review and meta-analysis of comparative studies. Int Braz J Urol. 2022;48(6):903–914. doi:10.1590/S1677-5538.IBJU.2022.0225.

This page provides general information and is not a substitute for an individual assessment by a qualified health professional. If you have hydronephrosis, your clinician can explain what the scan means in your circumstances and whether further tests or treatment are needed.

Renal cysts: when to reassure, when to investigate and when to treat

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Renal cysts are fluid-filled sacs within or on the kidney. Finding a “cyst” on a scan can be worrying, but many are harmless. The important questions are whether the cyst has a simple or complex appearance, whether it is causing symptoms, and whether it affects urine drainage or kidney function.

A large simple cyst is not automatically cancerous, and a small complex cyst is not automatically harmless. Imaging features and the clinical situation guide management.

What types of renal cysts are there?

Simple cysts have a thin, smooth wall and contain fluid. They become more common with age and usually cause no symptoms or loss of kidney function. Most need no treatment.[1]

Complex cystic masses have additional features, such as internal partitions called septa, thickened walls or tissue nodules. “Complex” describes their appearance; it does not establish a cancer diagnosis.[2]

Parapelvic cysts lie beside the renal pelvis, the funnel that collects urine before it enters the ureter. Their location can make diagnosis and treatment more difficult.[6]

Polycystic kidney disease is a separate condition, often inherited, in which multiple cysts may enlarge the kidneys and affect kidney function. Numerous cysts in both kidneys, especially with a family history, merit assessment for cystic kidney disease rather than being assumed to be ordinary simple cysts.[9]

How do renal cysts present?

Most simple cysts are discovered incidentally during an ultrasound, CT or MRI performed for another reason.

Occasionally, a cyst causes a dull ache in the flank or back, pressure or discomfort, or obstruction to urine drainage. Bleeding, infection or rupture can cause more acute symptoms. Fever with flank pain may indicate infection.[1]

Pain and blood in the urine have many possible causes, including stones and other urinary tract conditions. Finding a cyst does not prove that it caused the symptoms. Visible blood in the urine should be assessed rather than attributed to a known cyst.

What investigations are needed?

Ultrasound often identifies an uncomplicated simple cyst. If the lesion is uncertain or complex, a dedicated contrast-enhanced CT or MRI can assess its wall, septa and any solid tissue. Contrast-enhanced ultrasound is another option in centres with appropriate expertise.[3]

An important finding is enhancement: tissue becomes brighter after contrast, indicating a blood supply. Enhancement in thickened or irregular tissue or a nodule raises concern.

Urine testing and blood tests for kidney function may be appropriate. Infection symptoms may require a urine culture. Contrast choices are individualised according to kidney function, allergies and other circumstances.

Ordinary ultrasound alone may not adequately classify a complex cyst. A radiology report should ideally state which version of the Bosniak classification has been used.[2,3]

Bosniak classification: understanding the scan report

The Bosniak system groups cystic renal masses by imaging appearance. The 2019 version incorporates CT and MRI criteria. It estimates concern for malignancy; it is not a cancer stage or a substitute for specialist assessment.[2]

Category Simplified meaning Usual approach
I Simple fluid-filled cyst with a thin, smooth wall Benign; no routine follow-up if confidently classified
II Benign features, such as a few thin septa or certain non-enhancing blood/protein-containing cysts Usually no routine follow-up
IIF More septa or mild smooth thickening; “F” means follow-up Scheduled imaging to check for change
III Enhancing thick or irregular walls or septa Indeterminate; specialist discussion of surveillance or treatment
IV An enhancing tissue nodule Strong concern for cancer; specialist assessment and treatment planning

This table is deliberately simplified. Calcification or blood within a cyst does not by itself establish cancer. The pattern of enhancement and tissue architecture matters.[2,3]

When should cancer be a concern?

Concern increases with enhancing nodules, irregular or thick enhancing walls/septa, or progression to a more suspicious category on follow-up.

Bosniak III masses include both benign and malignant lesions. Bosniak IV masses have a high likelihood of malignancy. Published percentages vary with the classification version and which patients undergo surgery, so a single percentage should not be treated as an individual prediction.[3,4]

Absence of symptoms does not exclude cancer. Conversely, enlargement of an otherwise simple cyst does not alone prove malignant change.

Follow-up and active surveillance

For Bosniak IIF lesions, the Canadian Urological Association suggests imaging at 6–12 months during the first year, then annually if stable, for a total of five years without progression.

Its 2023 guideline also supports active surveillance as a preferred option for selected Bosniak III/IV masses measuring 2 cm or less; surveillance or surgery for those measuring 2–4 cm; and surgery generally for those larger than 4 cm. These recommendations have limited-certainty evidence and require shared decision-making.[4]

Other guidelines differ in emphasis. The EAU allows surveillance for selected Bosniak III lesions and generally manages Bosniak IV lesions as localised kidney cancer.[8] Age, overall health, kidney function, imaging features and patient preferences all matter.

Surveillance means planned scans and reassessment, with treatment considered if concern increases. Biopsy may help when there is a targetable solid component and the result would change management; sampling a mainly fluid-filled lesion often has a low diagnostic yield.[4]

When should a benign cyst be treated?

Treatment may be considered for persistent symptoms convincingly attributable to the cyst, obstruction, or complications such as infection. There is no universal size threshold requiring treatment for a confidently benign simple cyst.[1]

Before intervention, the team should establish that the lesion is benign and discuss whether treatment is likely to relieve the symptoms.

Treatment options

Interventional radiology: aspiration and sclerotherapy

An interventional radiologist can use ultrasound or CT to guide a needle or catheter into a suitable simple cyst. The fluid is drained, usually under local anaesthetic, sometimes with sedation.

Aspiration alone can provide temporary relief, but the cyst may refill. Sclerotherapy adds an agent to damage the fluid-producing lining and reduce recurrence. The team must exclude communication with the urine collecting system before using a sclerosant.

A systematic review of 57 studies reported treatment success in approximately 88% of patients receiving aspiration with sclerotherapy, defined as symptom resolution together with more than 50% cyst-size reduction. Techniques and study quality varied; this is not a guarantee for an individual patient.[5]

Risks include pain, bleeding, infection, leakage of the agent, injury to nearby structures and recurrence. Repeat treatment may be needed.

Laparoscopic cyst deroofing

Deroofing, also called decortication, removes part of the cyst wall so it cannot readily reform as a closed sac. The removed tissue is usually sent for pathology.

Performed through small incisions under general anaesthesia, it may suit large, accessible symptomatic cysts or cysts that recur after percutaneous treatment.

A comparative meta-analysis found lower treatment-failure rates with laparoscopic deroofing than aspiration with sclerotherapy, while percutaneous treatment generally involved shorter procedures, shorter hospital stays and fewer complications.[7]

Surgical risks include bleeding, infection, injury to nearby organs or the collecting system, urine leakage, persistent pain and recurrence. Recovery depends on the procedure and the patient’s health.

Robotic-assisted deroofing

Robotic assistance is another way to perform minimally invasive cyst surgery. It may help with dissection in selected cases, but the robot is operated by the surgeon. Its availability does not mean it is necessary or offers a better result for every cyst. Location, complexity, expertise and cost should guide the choice.[7]

If the cyst is suspicious for cancer

Simple drainage or deroofing is not an appropriate cancer operation. Management may involve surveillance, partial nephrectomy to remove the lesion while preserving kidney tissue, or occasionally removal of the whole kidney. Ablation may be considered in selected patients, although evidence for complex cystic lesions is limited.[4,8]

I no longer perform nephrectomies. If partial or radical nephrectomy is indicated, I will refer you to a colleague who performs this surgery.

Parapelvic cysts: a special situation

Parapelvic cysts are beside the kidney’s central urine collecting system and usually do not communicate with it. They can mimic hydronephrosis, a dilated collecting system, on ultrasound. Contrast imaging, sometimes including delayed images, can distinguish the two and show whether a cyst is compressing urine drainage.[6]

Many asymptomatic benign parapelvic cysts can be observed. Treatment may be considered when a cyst causes pain or demonstrable obstruction.

Options include carefully planned laparoscopic or robotic deroofing, or ureteroscopic internal drainage in selected cases. With ureteroscopy, a telescope passes through the urethra, bladder and ureter into the kidney; a laser opens the cyst into the collecting system. A temporary ureteric stent may be required. Published studies support feasibility, but long-term comparative evidence remains limited.[6,10]

Sclerotherapy is generally avoided for parapelvic cysts because leakage or inflammation near the collecting system can cause scarring and obstruction. Any proposed percutaneous approach requires specialist assessment; routine simple-cyst treatment should not be applied automatically.[6]

Their proximity to blood vessels and the collecting system also increases the technical difficulty of surgery. Risks include bleeding, urine leakage, infection, narrowing and recurrence.

When to seek prompt medical attention

Seek urgent assessment for severe flank pain with fever or rigors, significant bleeding or clots in the urine, difficulty passing urine, or pain accompanied by faintness or marked illness. Persistent visible blood in the urine also requires medical review.

References

  1. National Institute of Diabetes and Digestive and Kidney Diseases. Simple kidney cysts.
  2. Silverman SG, et al. Bosniak Classification of Cystic Renal Masses, Version 2019: An Update Proposal and Needs Assessment. Radiology. 2019;292:475–488. Article.
  3. European Association of Urology. Renal Cell Carcinoma Guidelines: Diagnostic evaluation.
  4. Canadian Urological Association. 2023 update: Management of cystic renal lesions. Canadian Urological Association Journal. Guideline.
  5. Brown D, et al. Radiologically guided percutaneous aspiration and sclerotherapy of symptomatic simple renal cysts: a systematic review of outcomes. Abdominal Radiology. 2021. PubMed.
  6. Ureteroscopic management of asymptomatic and symptomatic simple parapelvic renal cysts. BMC Urology. 2015. Article.
  7. Comparison of aspiration with sclerotherapy and laparoscopic deroofing for the treatment of symptomatic simple renal cysts: a systematic review and meta-analysis. Updates in Surgery. 2021. PubMed.
  8. European Association of Urology. Renal Cell Carcinoma Guidelines: Epidemiology, aetiology and pathology and Disease management.
  9. NIDDK. What is polycystic kidney disease?.
  10. Transurethral flexible ureteroscopic incision and drainage with holmium laser in the treatment of parapelvic renal cysts. International Brazilian Journal of Urology. 2022. Article.

General patient education. Individual management depends on imaging findings, symptoms, kidney function and discussion with the treating team. Reviewed October 2026.

Nephroptosis: is a “floating kidney” really a thing?

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Can a kidney move enough to cause pain? Yes. Nephroptosis is a recognised anatomical condition, and in selected people it can cause symptoms. However, finding a mobile kidney does not automatically explain abdominal or flank pain. Establishing that connection is the central challenge, and the reason this condition has attracted controversy for more than a century.[1,2]

What is nephroptosis?

The kidneys normally sit towards the back of the abdomen, supported by surrounding fat and connective tissues. Some movement with breathing and changes in posture is normal.

Nephroptosis, also called a floating or mobile kidney, is conventionally defined as downward movement of more than 5 cm, or approximately two vertebral body heights, when a person moves from lying down to standing. A kidney can also rotate or move towards the midline.[3,4]

This differs from a congenital pelvic kidney, which developed in a lower position and stays there.

Published reports describe it more often in slim women and more often on the right, although men and people with other body types can be affected. Reduced support from surrounding fat is a proposed contributor. The true prevalence of symptomatic nephroptosis is uncertain; historical figures from people undergoing particular imaging tests should not be treated as estimates for the general population.[4]

How does it present?

Many mobile kidneys cause no symptoms. When symptoms occur, a suggestive pattern is:

  • An ache, dragging sensation or intermittent pain in the flank, the side between the lower ribs and hip, or abdomen.
  • Pain that becomes worse with standing, prolonged activity or particular positions.
  • Improvement when lying down.
  • Occasionally, a feeling of something moving within the abdomen.

Some patients experience more severe episodes with nausea or vomiting. Positional pain is a useful clue, but it does not establish the diagnosis.[2,5]

Possible mechanisms include intermittent kinking of the ureter, which drains urine to the bladder; stretching or twisting of the kidney’s blood vessels; or traction on nerves around the kidney. These mechanisms may differ between patients. Severe episodic pain from intermittent upper urinary tract obstruction is sometimes called a Dietl’s crisis, but that term is not specific to nephroptosis.[4,5]

Blood in the urine or urinary infections require investigation in their own right and should not simply be attributed to a mobile kidney.

How is the diagnosis made?

There are two separate questions: Does the kidney move excessively? And is that movement responsible for symptoms or impaired function?

1. Establish the symptom pattern and assess other causes

A consultation should explore where the pain occurs, its relationship to posture and activity, what relieves it, and associated urinary or gastrointestinal symptoms. Examination, urine testing and blood tests for kidney function help guide the investigation.

Other explanations include kidney stones, infection, obstruction at the junction between the kidney and ureter, musculoskeletal pain, and gastrointestinal or gynaecological conditions. Depending on the presentation, these may be more likely. A mobile kidney can coexist with an unrelated cause of pain.[2,3]

2. Compare imaging in different positions

A normal scan performed lying down may not exclude a problem that occurs when upright. If the clinical pattern raises suspicion, the imaging request should make the positional question explicit.[3,5]

Investigation What it can contribute Main limitation
Ultrasound lying down and upright Demonstrates movement and checks for changes in collecting-system dilatation Operator dependent; requires a deliberate positional examination
Doppler ultrasound in different positions May identify posture-related changes in renal blood flow An adjunct rather than a definitive test of the cause of pain
Positional nuclear medicine renal scan Assesses drainage and each kidney’s contribution to function; may reveal changes when upright Needs an appropriate protocol and careful interpretation
Intravenous urography with supine and erect images Historically used to measure kidney descent Used less often today; involves radiation and contrast
Selected positional CT urography Can clarify anatomy, rotation or medial movement Routine supine CT may miss positional mobility; repeat imaging adds radiation

The choice should be agreed with radiology or nuclear medicine. Not every centre routinely performs these protocols, and not every patient needs every test.[3,5,6]

3. Link the findings to the symptoms

Diagnostic confidence is stronger when the side and timing of the pain match the demonstrated movement, particularly if there is associated impaired drainage or blood flow. Nevertheless, some symptomatic patients have no demonstrable obstruction. The absence of obstruction does not conclusively exclude symptomatic nephroptosis, but it makes careful exclusion of other causes especially important.[3,4,6]

Normal overall kidney function does not, by itself, exclude an intermittent positional problem. Equally, descent beyond a measurement threshold is not sufficient justification for surgery.[2,5]

What are the treatment options?

Observation and symptom management

An incidentally discovered mobile kidney without symptoms or functional consequences generally does not require surgery.[5]

For mild symptoms, an individual plan may include modifying provoking activities, appropriate pain relief and reviewing other possible contributors. Abdominal supports, exercises and nutritional measures have been used historically, but convincing evidence that they reliably correct symptomatic nephroptosis is limited. They should not be presented as proven cures. Weight gain is not a universal recommendation.[1,2]

Nephropexy: fixing the kidney in position

Nephropexy repositions the kidney and secures it to surrounding tissues to limit excessive movement. It aims to preserve the kidney and relieve symptoms or positional impairment.

It may be considered when symptoms substantially affect daily life, nephroptosis has been demonstrated with appropriate imaging, other explanations have been reasonably excluded, and the evidence suggests a meaningful relationship between movement and symptoms. Documented positional obstruction or impaired perfusion strengthens the rationale.[2,3,5]

Modern surgery is usually laparoscopic, through the abdomen or behind it. Robotic assistance has also been described, but there is no convincing comparative evidence that it produces better outcomes than conventional laparoscopy for this condition. Fixation techniques vary, and some published methods use mesh while others use sutures.[3]

Open surgery is less commonly used. Percutaneous techniques, intended to stabilise the kidney through a tract and subsequent scarring, have also been reported. A recent report involved only four patients: such evidence is too limited to establish equivalence with laparoscopic surgery or support routine use.[7]

How effective is surgery, and what are the risks?

Small surgical series describe substantial improvement in selected patients. For example, a long-term study reported 13 patients assessed at a median of 5.9 years: 11 were completely satisfied and two moderately satisfied.[8]

That is encouraging, but it is not a reliable prediction for every patient. Small numbers, selection of patients, loss to follow-up and the absence of a non-operative comparison group limit what can be concluded. Fixing the kidney successfully does not guarantee that pain will disappear.[2,8]

Potential risks include bleeding, infection, injury to nearby organs, vessels or the urinary tract, anaesthetic complications, persistent or new pain, and recurrent kidney movement. If mesh is proposed, its specific benefits and risks should be discussed. Individual risks and expected recovery depend on the technique and the patient’s circumstances.

Why is nephroptosis controversial?

The controversy concerns which patients have symptoms caused by kidney mobility, and which benefit from treatment.

Historically, nephroptosis was blamed for a wide range of nonspecific symptoms, and nephropexy was performed much more frequently than it is today. Recognition that many mobile kidneys were harmless, together with inconsistent surgical results, led to scepticism and a marked decline in treatment.[1]

Modern positional imaging and minimally invasive surgery have renewed interest. However, the evidence remains dominated by small observational series and case reports rather than robust randomised comparisons. There is also no universally accepted combination of symptoms and test findings that predicts success for an individual.[2,6,8]

The appropriate response is to take the symptoms seriously while investigating the cause carefully. A normal routine scan does not mean pain is imagined. A mobile kidney does not mean an operation will solve it.

When should you seek urgent care?

Severe or escalating flank pain, fever or rigors, persistent vomiting, visible blood in the urine, or a marked reduction in urine output warrant prompt medical assessment. These symptoms can signal infection, obstruction or another problem requiring urgent treatment, regardless of whether nephroptosis is present.

This article provides general education. Diagnosis and treatment require an individual clinical assessment.

Patient information by Dr Jo Schoeman | Evidence reviewed October 2026

References

  1. Moss SW. Floating kidneys: a century of nephroptosis and nephropexy. Journal of Urology. 1997;158(3 Pt 1):699–702. doi:10.1016/S0022-5347(01)64296-4.
  2. Barber NJ, Thompson PM. Nephroptosis and nephropexy—hung up on the past? European Urology. 2004;46(4):428–433. doi:10.1016/j.eururo.2004.03.023.
  3. Mogorovich A, Selli C, De Maria M, et al. Clinical reappraisal and state of the art of nephropexy. Urologia. 2018;85(4). doi:10.1177/0391560317749191.
  4. Senaratne R, Anderson S, Kelly C, et al. Rolling in the deep: an illustrative report of symptomatic nephroptosis. Radiology Case Reports. 2024;19(9):4044–4048. doi:10.1016/j.radcr.2024.06.047. Case report.
  5. Murari SB, Gadepalli T, Rao VP, Ram R. Renal scintigraphy in diagnosis and management of nephroptosis. Indian Journal of Nuclear Medicine. 2012;27(1):52–54. doi:10.4103/0972-3919.108874. Case report.
  6. Strohmeyer DM, Peschel R, Effert P, et al. Changes of renal blood flow in nephroptosis: assessment by color Doppler imaging, isotope renography and correlation with clinical outcome after laparoscopic nephropexy. European Urology. 2004;45:790–793. PubMed.
  7. Liu H, Gao W, Zhang Z, et al. Modified percutaneous nephropexy for nephroptosis: technical description and short-term results. Current Urology. 2025;19(3):168–172. doi:10.1097/CU9.0000000000000238. Small technical series; four patients.
  8. Plas E, Daha K, Riedl CR, Hübner WA, Pflüger H. Long-term followup after laparoscopic nephropexy for symptomatic nephroptosis. Journal of Urology. 2001;166(2):449–452. PubMed.

Small renal masses: observation, surgery and image-guided ablation

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An unexpected spot on a kidney scan can be alarming. A small renal mass usually means a solid, enhancing growth measuring 4 cm or less and confined to the kidney. It is not automatically cancer: some are benign, and many small kidney cancers grow slowly. The right approach depends on the scan, any biopsy result, kidney function, other health conditions and what matters to you. [1,2]

How do we investigate it?

I review the original imaging and usually arrange a dedicated, multiphase contrast CT or MRI to establish whether the lesion enhances, its size and position, and whether it looks like a simple cyst or another benign condition. Blood tests assess kidney function. The need for chest imaging depends on the findings and clinical circumstances. If contrast is unsuitable because of impaired kidney function, we plan an alternative with the radiologist. [1,2]

A needle biopsy can help when knowing whether a mass is benign or what type of cancer it contains would change the decision. A biopsy can occasionally be inconclusive. If ablation is planned, the European Association of Urology (EAU) recommends biopsy before a separate ablation session to avoid treating benign lesions unnecessarily. [1]

What are the choices?

Approach When it may suit Main consideration
Active surveillance A very small mass, particularly under 2 cm; slow growth; or a patient who prefers to defer treatment Planned scans and a clear trigger to reconsider treatment
Partial nephrectomy A mass requiring treatment when kidney-sparing surgery is technically suitable Removes the tumour and supplies a complete specimen, but requires an operation
Percutaneous ablation A selected small mass when treatment is indicated, especially if surgery carries greater risk or preserving kidney tissue is important Less invasive, but imaging follow-up is essential and repeat treatment may be needed
Radical nephrectomy A tumour that cannot reasonably be treated with a kidney-sparing approach Removes the whole kidney and may have a greater effect on kidney function

For masses under 2 cm, surveillance is often a sensible first option. For masses 2–4 cm, surveillance, partial nephrectomy and ablation may all deserve discussion. If surgery is appropriate, guidelines generally favour partial nephrectomy for a treatable small cancer. Frailty or limited life expectancy may make symptom-focused observation preferable. [1,2]

Surveillance is an active plan, not neglect. Scans are often repeated every 3–6 months initially and then every 6–12 months if stable, with timing adapted to the individual. Growth beyond 4 cm, repeated growth above approximately 5 mm a year, new concerning features or patient preference can prompt reconsideration; growth rate alone does not prove that a mass is dangerous. [2]

What is radiofrequency ablation (RFA)?

RFA destroys tissue by passing an electrical current through a thin probe, generating heat inside the mass. An interventional radiologist usually places the probe through the skin using CT or ultrasound guidance. Anaesthesia or sedation, patient positioning and sometimes fluid injected to protect nearby bowel are planned around the tumour’s location. The radiologist treats the mass and a small surrounding margin, then checks for immediate complications. Many patients have a short hospital stay, but arrangements vary. [1–3]

RFA is most established for small, accessible masses, particularly those up to 3 cm. A mass deep in the kidney, next to the urine-drainage system or bowel, or near major vessels can be harder to treat safely or completely. EAU guidance advises against routinely offering RFA for masses over 3 cm, because control becomes less reliable. A mass between 3 and 4 cm needs an individual discussion rather than an automatic exclusion. [1]

What other ablation methods are available?

  • Cryoablation uses probes to freeze the tumour. The visible ice ball can help the operator plan the treatment margin. It is an established alternative to RFA; the EAU advises against its routine use for tumours over 4 cm. [1,2]
  • Microwave ablation uses microwave energy to heat tissue. Experience is growing and the EAU describes encouraging results, though long-term comparative evidence remains less certain than for surgery. Availability and expertise vary. [1]
  • Irreversible electroporation delivers electrical pulses to disrupt cell membranes. Evidence for routine treatment of small renal cancers remains limited. [2]
  • Stereotactic ablative radiotherapy (SABR/SBRT) directs highly focused radiation without inserting a probe. It can be discussed for selected patients who need treatment but are unsuitable for surgery; long-term comparisons remain limited. [1]

The choice depends on tumour size and position, prior treatment, kidney function, local expertise and the patient’s preferences. No technique is right for every lesion.

Benefits, limitations and risks

Percutaneous ablation can avoid a surgical incision, usually involves less immediate recovery than surgery and can preserve functioning kidney tissue. Risks include bleeding, infection, pain, injury to the urine-collecting system or nearby organs, and incomplete treatment or local recurrence. Risks depend strongly on where the tumour sits. A second ablation or surgery may be possible if follow-up imaging shows persistent disease. [1,2]

Evidence comparing ablation with partial nephrectomy largely comes from observational studies involving patients with different health risks. Ablation offers good local control for carefully selected small tumours, but its long-term cancer control relative to surgery is less certain; it should not be described as a guaranteed equivalent. [1,2]

What happens after ablation?

Treatment destroys the lesion in place, so there is no whole-tumour surgical specimen. Contrast-enhanced CT or MRI checks for remaining enhancing tissue and later recurrence. One published guideline suggests imaging at 3, 6 and 12 months, then annually after ablation, adjusted to biopsy findings, renal function and the treating team’s protocol. We also monitor kidney function. A new enhancing focus requires specialist review and may lead to repeat biopsy or treatment. [1,2]

My role in your care

I can review the findings and discuss surveillance, biopsy and the treatment choices with you. I no longer perform nephrectomies. If an operation is the best option, I will refer you to a colleague who performs kidney surgery. If ablation appears suitable, I will arrange assessment by an experienced interventional radiology team; the final decision follows review of the images and your overall health.

Seek urgent medical attention for heavy visible bleeding, inability to pass urine, fever with flank pain, or severe worsening pain after a procedure.

This article provides general information. Individual advice requires assessment of your imaging, biopsy findings where relevant, kidney function and medical history.

Dr Jo Schoeman | Patient information | September 2026

References

  1. European Association of Urology. EAU Guidelines on Renal Cell Carcinoma: Disease Management, current online edition, accessed September 2026.
  2. Richard PO, et al. Canadian Urological Association guideline: Management of small renal masses. Canadian Urological Association Journal. 2022;16(2)–E75.
  3. Park BK, et al. Asian Conference on Tumor Ablation guidelines for renal cell carcinoma. Investigative and Clinical Urology. 2021.
  4. European Association of Urology. EAU Guidelines on Renal Cell Carcinoma: Follow-up, current online edition, accessed September 2026.

A kidney tumour larger than 3 cm: what does it mean?

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By Dr Jo Schoeman | Patient information | September 2026

Finding a kidney mass can be frightening. The first question is whether it is cancer; the next is whether it is confined to the kidney. A mass measuring 3.1 cm is not automatically advanced cancer. If a renal cell carcinoma (RCC) is no more than 4 cm and remains within the kidney, it is classified as T1a. A tumour over 4 cm but no more than 7 cm, still confined to the kidney, is T1b. Lymph-node and distant spread are assessed separately. Some kidney masses are benign, and imaging alone cannot always tell us which. [1–3]

How might it present?

Many tumours are discovered by chance during an ultrasound or CT scan for another problem. Others cause blood in the urine, persistent pain in the side or back, or occasionally a palpable lump. Unexplained weight loss, fatigue, anaemia or fever warrant assessment, although they have many possible causes. The combination of blood in the urine, pain and a palpable mass is uncommon. Visible blood in the urine should always be investigated; a kidney mass does not rule out another source of bleeding. [2]

What investigations are needed?

  • Dedicated imaging: A multiphase contrast CT of the kidneys and abdomen shows whether the lesion enhances, its exact position, its relationship to major blood vessels and the collecting system, and whether there are enlarged nodes or signs of spread. Chest imaging completes staging; its extent is tailored to the tumour and clinical circumstances. MRI may clarify an uncertain lesion or suspected tumour extension into a vein, or be useful when CT contrast is unsuitable. A complex kidney cyst needs its own imaging assessment. [2]
  • Blood and urine tests: Kidney function (creatinine and eGFR), a full blood count and other tests guided by the clinical picture help assess fitness for treatment and preserve kidney function. Urine testing may identify infection or another cause of bleeding. [2]
  • Biopsy: A needle biopsy can be useful if its result will change management, particularly before ablation or drug treatment without prior tissue diagnosis. A typical surgically removable solid mass does not always need a biopsy beforehand. A biopsy can occasionally be inconclusive. [2]
  • Further staging: Bone or brain scans are generally reserved for relevant symptoms or suspected advanced disease. Routine PET scans and bone scans are not recommended for initial RCC staging. [2]

The team should review the images, kidney function, other medical conditions and the patient’s priorities together. An indeterminate mass should not be labelled definitively as RCC before appropriate assessment.

A note about my practice: I no longer perform nephrectomies. I can assess your kidney mass, discuss the findings and treatment options with you, and, if an operation is appropriate, refer you to a colleague who performs kidney surgery. We can also arrange input from a multidisciplinary team where needed.

Treatment when the tumour is confined to the kidney

Partial nephrectomy removes the tumour while preserving the rest of the kidney. This is generally preferred for T1 cancers when technically feasible, particularly if kidney function is reduced or there is only one functioning kidney. It can be performed by robotic, laparoscopic or open surgery according to tumour complexity and surgical expertise. Risks include bleeding, urine leak, infection, reduced kidney function and, occasionally, the need to remove the whole kidney. [1]

Radical nephrectomy removes the kidney and may be appropriate when a safe partial nephrectomy is not feasible, particularly with a larger or more complex tumour. Robotic or laparoscopic surgery offers an approach to the operation; it does not change the underlying choice between partial and radical removal. [1]

Active surveillance may suit selected people with a small, slow-growing mass, competing health risks or a strong preference to defer treatment. It involves planned scans and a clear trigger to reconsider treatment. A tumour just above 3 cm needs a particularly careful discussion because the room for further growth before 4 cm is limited. Thermal ablation, such as cryoablation or radiofrequency or microwave ablation, may suit selected small tumours, especially when surgery is unsuitable; a biopsy is recommended before ablation. Local recurrence and the possible need for repeat treatment should be discussed. [1, 2]

Stereotactic ablative radiotherapy (SABR) is also being used in specialist centres for selected patients with localised RCC who cannot undergo surgery. It is a distinct option from routine radiation after an operation, and its long-term comparative evidence continues to mature. [1]

What if lymph nodes look enlarged?

An enlarged node on a scan is suspicious, not proof of cancer; inflammation can also enlarge nodes. The team considers the appearance and site of the nodes, whether there is disease elsewhere and whether tissue confirmation will change treatment. If nephrectomy is planned, visibly enlarged regional nodes may be removed for diagnosis and staging. Removing normal-looking nodes routinely has not been shown to improve survival for organ-confined RCC. The survival benefit of removing involved nodes is uncertain. [1]

Confirmed regional node involvement is a substantial change in risk even if the kidney tumour is small. It calls for multidisciplinary discussion about whether all visible disease can be removed, whether postoperative drug treatment is appropriate, and how closely to monitor. Nodes beyond the regional area, or spread to organs such as the lung or bone, may represent metastatic disease and require a different plan. Surgery on the kidney is not automatically the best first step when cancer is widespread. [1, 3]

When does immunotherapy help?

For selected patients with clear-cell RCC at higher risk of recurrence after complete surgery, a course of pembrolizumab may lower recurrence risk and has shown an overall survival benefit in the KEYNOTE-564 study. The eligible groups include some patients with confirmed regional node involvement and no distant metastases. A 3–4 cm node-negative tumour confined to the kidney would not usually qualify based on size alone. The final pathology, stage and overall health matter. [1, 4]

If cancer has spread and cannot all be removed, initial treatment for clear-cell RCC often combines immune checkpoint drugs with each other (nivolumab plus ipilimumab) or combines immunotherapy with an oral targeted drug (for example, pembrolizumab plus axitinib, pembrolizumab plus lenvatinib, or nivolumab plus cabozantinib). The best regimen depends on risk group, other illnesses, kidney function, previous treatment and the specific cancer subtype. Papillary and other non-clear-cell cancers may need different approaches. Availability and subsidy in Australia should be checked for the individual indication. [1]

Immunotherapy can cause serious inflammation of the bowel, lungs, liver, kidneys or hormone-producing glands; targeted drugs can cause high blood pressure, diarrhoea, fatigue and other adverse effects. Some immune effects can persist after treatment ends. Benefits and risks need an individual discussion with a medical oncologist. [1, 4]

Is chemotherapy useful?

Conventional cytotoxic chemotherapy is generally ineffective for the common types of RCC and is not standard treatment for ordinary clear-cell RCC. Rare subtypes, including collecting duct and renal medullary carcinoma, are exceptions in which chemotherapy may have a role. A cancer arising from the lining of the renal pelvis (upper-tract urothelial carcinoma) is a different disease with different chemotherapy options; establishing the diagnosis matters. [1]

Does radiation offer a benefit?

Radiotherapy is not routinely given after nephrectomy to prevent recurrence of localised RCC. Its clearest established role is treating specific problems from spread, such as painful bone lesions, brain metastases or symptoms from another site. Precisely targeted radiation may also control selected limited metastases or treat a primary tumour in someone unsuitable for surgery. Whether it adds benefit to systemic therapy or surgery in an individual case depends on the site, number and behaviour of lesions and is best decided with radiation oncology input. It should not be presented as a standard substitute for an operable partial nephrectomy. [1, 5]

Questions worth asking at your consultation

  1. Is this definitely a solid enhancing kidney tumour, and what is its exact size and location?
  2. Is the disease confined to the kidney? Are any nodes merely enlarged, or proven to contain cancer?
  3. Can we safely preserve part of the kidney? What is my current kidney function?
  4. Would a biopsy change the plan?
  5. If the cancer is clear-cell and higher risk, would adjuvant pembrolizumab be suitable?
  6. Would drug treatment or targeted radiation offer a benefit in my particular situation?

Seek prompt medical attention for heavy bleeding with clots, inability to pass urine, severe persistent pain, or sudden neurological symptoms. This article is general information and cannot replace review of your scans and pathology at a multidisciplinary meeting.

References

  1. European Association of Urology. EAU Guidelines on Renal Cell Carcinoma: Disease Management. 2026.
  2. European Association of Urology. EAU Guidelines on Renal Cell Carcinoma: Diagnostic Evaluation. 2026.
  3. European Association of Urology. EAU Guidelines on Renal Cell Carcinoma: Staging and Classification Systems. 2026.
  4. National Cancer Institute. Adjuvant Keytruda improves kidney cancer survival, reporting updated KEYNOTE-564 outcomes. 2024.
  5. National Cancer Institute. Renal Cell Cancer Treatment (PDQ), Health Professional Version. Accessed September 2026.

Information Sheet: Renal Cancers

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Upper Tract Urothelial Carcinoma

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Cancer of the Renal Pelvis and Ureter

Urothelial carcinoma is most commonly associated with the bladder, but the same specialised lining extends all the way from the bladder up the ureters and into the collecting system of each kidney.

When a urothelial cancer develops in the renal pelvis or ureter, it is called upper tract urothelial carcinoma (UTUC).

UTUC is considerably less common than bladder cancer. Importantly, its behaviour varies enormously. Some tumours are small, superficial and relatively slow growing, while others are aggressive cancers capable of invading the kidney, surrounding tissues, lymph nodes and distant organs.

The key to successful management is therefore not simply finding the tumour, but determining how aggressive it is and how likely it is to spread.

What Is the Upper Urinary Tract?

Urine produced by the kidney drains through:

Kidney → renal calyces → renal pelvis → ureter → bladder → urethra

The inner surface of the renal pelvis, ureter and bladder is covered by urothelium, previously called transitional epithelium.

Cancer arising from these cells is called urothelial carcinoma.

UTUC can therefore occur in:

  • the renal pelvis;
  • one or more renal calyces;
  • the upper, middle or lower ureter;
  • multiple areas of the same urinary tract; or
  • occasionally both upper urinary tracts.

Patients with UTUC may also develop urothelial tumours within the bladder, either at the same time or later.

What Causes Upper Tract Urothelial Cancer?

Cancer develops when genetic damage accumulates within urothelial cells, allowing them to grow and divide abnormally.

Frequently there is no single identifiable cause, but several important risk factors are recognised.

Smoking

Cigarette smoking is one of the most important preventable risk factors for urothelial carcinoma.

Carcinogenic chemicals absorbed through the lungs enter the bloodstream, are filtered by the kidneys and become concentrated in the urine. The urothelium may therefore be exposed to these substances for many years.

Stopping smoking remains important even after diagnosis because of its wider health benefits and potential relevance to future urothelial cancer risk.

Previous bladder cancer

Patients who have previously had urothelial carcinoma of the bladder have an increased risk of developing urothelial carcinoma elsewhere within the urinary tract.

Similarly, patients treated for UTUC remain at risk of subsequently developing bladder cancer.

Occupational chemical exposure

Long-term exposure to certain industrial chemicals, particularly some aromatic amines historically associated with dye, rubber, textile, leather and chemical industries, has been associated with urothelial cancer.

Lynch syndrome

A small but important proportion of UTUC occurs in people with Lynch syndrome, an inherited disorder caused by abnormalities in DNA mismatch-repair genes.

UTUC, particularly in a younger patient or someone with a strong family history of bowel, endometrial or other Lynch-associated cancers, may prompt consideration of genetic assessment.

Chronic inflammation

Long-standing urinary tract inflammation and some chronic infections may contribute to malignant change. Chronic stone disease has particularly been associated with squamous carcinoma of the renal pelvis, which is a different and much less common tumour type.

Previous analgesic exposure

Heavy historical exposure to certain analgesics, particularly phenacetin-containing preparations that are no longer routinely used in many countries, has been associated with upper tract urothelial malignancy.

What Are the Symptoms?

Blood in the urine

The most common warning sign is:

Haematuria: blood in the urine

This may be obvious, turning the urine pink, red or occasionally dark brown.

Importantly, haematuria may:

  • occur only once;
  • disappear for weeks or months;
  • be completely painless; or
  • only be detected microscopically on a urine test.

Visible blood in the urine should always be appropriately investigated, particularly in adults.

Do not assume that painless bleeding is simply due to infection, prostate enlargement or a blood-thinning medication without appropriate assessment.

Flank or loin pain

A tumour can obstruct drainage of urine from the kidney.

This may produce:

  • persistent flank discomfort;
  • loin pain;
  • renal colic;
  • hydronephrosis, where the kidney becomes dilated because urine cannot drain normally.

Blood clots passing down the ureter can occasionally produce severe colicky pain resembling a kidney stone.

Recurrent urinary symptoms

Some patients experience:

  • urinary frequency;
  • urgency;
  • burning when passing urine;
  • recurrent apparent urinary tract infections.

These symptoms are much more commonly caused by benign conditions, but persistent or unexplained symptoms may warrant further investigation.

General symptoms

More advanced disease can occasionally cause:

  • unexplained weight loss;
  • loss of appetite;
  • fatigue;
  • persistent pain;
  • anaemia.

Fortunately, many tumours are detected before these symptoms develop.

How Is UTUC Diagnosed?

Investigation usually involves several complementary tests.

1. Urine testing

Urine is assessed for:

  • microscopic blood;
  • infection;
  • renal abnormalities; and
  • sometimes malignant cells.

Urine cytology

Urine cytology examines shed urinary cells under a microscope.

It is particularly useful for detecting high-grade urothelial carcinoma, although a negative cytology result does not completely exclude cancer.

Selective urine samples may sometimes be collected directly from the affected upper urinary tract.

2. CT Urography

CT urography is one of the most important imaging investigations for suspected UTUC.

Contrast-enhanced CT imaging allows assessment of:

  • the kidneys;
  • renal collecting systems;
  • ureters;
  • bladder;
  • lymph nodes; and
  • surrounding organs.

A tumour may appear as a filling defect, thickening of the ureter or renal pelvis, or an infiltrating mass.

CT can also identify obstruction and hydronephrosis.

3. Cystoscopy

Because urothelial cancer can occur at more than one location, the bladder should generally also be examined.

A flexible cystoscope is passed through the urethra into the bladder to look for associated bladder tumours.

Ureteroscopy and Biopsy

Sometimes imaging alone cannot provide enough information about the tumour.

A ureteroscope is a very fine telescope passed through the urethra and bladder and then into the ureter and renal collecting system.

This allows the urologist to directly inspect the tumour.

During ureteroscopy it may be possible to:

  • identify the location of the tumour;
  • assess whether there is one tumour or several;
  • estimate its size;
  • obtain selective urine cytology;
  • take a biopsy; and
  • in selected low-risk tumours, treat the lesion with a laser.

Biopsy is particularly helpful in determining whether the tumour is low-grade or high-grade.

An important limitation is that ureteroscopic biopsy samples are small, so determining the exact depth of invasion before definitive surgery can sometimes be difficult.

Low-Risk Versus High-Risk Disease

Modern management increasingly divides UTUC according to its risk of invasion and progression.

Factors considered include:

  • tumour grade;
  • appearance on CT;
  • tumour size;
  • number of tumours;
  • presence of hydronephrosis;
  • urine cytology;
  • ureteroscopic appearance;
  • biopsy findings;
  • evidence of invasion; and
  • previous urothelial cancer.

This distinction is extremely important because treatment can range from relatively conservative endoscopic therapy to removal of the entire kidney and ureter.

Treatment of Low-Risk UTUC

Selected patients with low-risk disease may be suitable for kidney-sparing treatment.

The objective is to control the cancer while preserving as much functioning kidney tissue as possible.

Ureteroscopic Laser Treatment

A ureteroscope is passed to the tumour and the lesion is treated using laser energy.

Laser treatment can:

  • vaporise;
  • coagulate; or
  • fragment the tumour.

Modern flexible ureteroscopes allow access to much of the renal collecting system.

Advantages

Kidney-sparing treatment may:

  • preserve kidney function;
  • avoid major abdominal surgery;
  • reduce recovery time;
  • be particularly valuable in patients with impaired kidney function or a solitary kidney.

Disadvantages

The trade-off is the need for very careful surveillance.

UTUC has a tendency to recur, so patients may require repeated:

  • ureteroscopy;
  • urine cytology;
  • CT imaging; and
  • occasionally further laser treatments or biopsies.

Kidney preservation therefore does not mean that the tumour can simply be treated once and forgotten.

Segmental Ureterectomy

Some tumours confined to a relatively short section of ureter can be treated by removing only the affected portion.

This is known as segmental ureterectomy.

It is particularly useful for appropriately selected tumours of the distal ureter.

The affected segment is removed and the remaining ureter is either reconnected or reimplanted into the bladder.

This can preserve the kidney while providing a complete surgical specimen for pathological examination.

Treatment of High-Risk UTUC

For patients with high-risk localised disease, the standard definitive operation is generally:

Radical Nephroureterectomy

This involves removal of:

the kidney + entire ureter + a cuff of bladder surrounding the ureteric opening

Removing the complete ureter is important because leaving part of the affected ureter behind may allow cancer to recur within the remaining urothelium.

The procedure can often be performed using:

  • robotic surgery;
  • laparoscopic surgery; or
  • occasionally open surgery.

The choice depends upon tumour characteristics, anatomy, previous surgery and individual circumstances.

What About the Lymph Nodes?

For selected high-risk tumours, lymph nodes draining the affected area may also be removed.

A lymph-node dissection can provide important staging information and may be incorporated into the surgical management of appropriately selected high-risk disease.

Chemotherapy

Systemic chemotherapy plays an important role in selected patients with higher-risk UTUC.

Platinum-based chemotherapy, particularly cisplatin-containing treatment, has traditionally formed an important part of systemic treatment.

Chemotherapy may be given:

Before surgery: neoadjuvant chemotherapy

One potential advantage is that both kidneys are still present, and renal function may therefore be better able to tolerate cisplatin.

After surgery: adjuvant chemotherapy

Chemotherapy may be recommended after nephroureterectomy when the final pathology demonstrates sufficiently high-risk disease.

An important consideration is that removing a kidney can reduce renal function, potentially affecting the patient’s ability to receive certain chemotherapy drugs.

Treatment decisions are therefore ideally made by a multidisciplinary uro-oncology team.

Immunotherapy and Newer Treatments

The treatment of advanced urothelial carcinoma has changed considerably in recent years.

Depending upon the stage, previous treatment and molecular characteristics of the cancer, systemic therapy may include combinations of:

  • platinum-based chemotherapy;
  • immune checkpoint inhibitors;
  • antibody-drug conjugates; and
  • targeted treatments for selected molecular abnormalities such as FGFR alterations.

These treatments are particularly relevant to patients with locally advanced, recurrent or metastatic disease.

Treatment is increasingly individualised according to the biological characteristics of the tumour and the patient’s kidney function and overall health.

Treatment Placed Directly Into the Upper Urinary Tract

For carefully selected non-invasive disease, medication may sometimes be delivered directly into the renal pelvis and ureter.

Options can include topical chemotherapy or immunotherapy in selected circumstances.

A chemoablative gel formulation of mitomycin has also been developed for selected low-grade UTUC, allowing prolonged contact between chemotherapy and the tumour.

These treatments are specialised and are not suitable for every patient.

What Happens After Treatment?

Follow-up is particularly important because urothelial carcinoma has a characteristic ability to develop at another point along the urinary tract.

After treatment, surveillance may include:

  • cystoscopy;
  • urine cytology;
  • CT urography or other upper-tract imaging;
  • blood tests to assess kidney function;
  • ureteroscopy following kidney-sparing treatment.

The exact surveillance schedule depends upon whether the original tumour was low or high risk and what treatment was performed.

Can the Cancer Return in the Bladder?

Yes.

One of the distinctive features of UTUC is the significant risk of subsequently developing urothelial carcinoma within the bladder.

Published data have reported subsequent bladder tumours in a substantial proportion of patients following treatment of UTUC.

For this reason, regular cystoscopic surveillance remains important even when the original kidney or ureteric tumour has been completely removed.

What Is the Prognosis?

The outlook for UTUC depends predominantly upon:

  • tumour stage;
  • tumour grade;
  • lymph-node involvement;
  • metastatic spread;
  • tumour multifocality;
  • response to treatment; and
  • certain pathological and molecular characteristics.

The most important question is whether the cancer remains superficial or has invaded deeply through the wall of the renal pelvis or ureter.

Superficial, localised disease

The outlook can be excellent when a tumour is identified while still superficial and confined to the upper urinary tract. The National Cancer Institute reports that more than 90% of superficial cancers confined to the renal pelvis or ureter may be curable.

Invasive disease

Once a tumour has invaded deeply into the wall or surrounding tissues, the risk of lymph-node involvement and distant spread increases substantially.

High-grade and invasive tumours therefore usually require more aggressive treatment and closer surveillance.

Metastatic disease

When UTUC has spread to distant organs, treatment is generally systemic rather than surgical alone.

Although metastatic UTUC remains a serious disease, modern systemic treatments have expanded considerably and can provide meaningful cancer control for selected patients.

UTUC and Kidney Function

Preserving kidney function is an important part of treatment planning.

Removing one kidney is usually well tolerated when the opposite kidney is healthy, but kidney function can become particularly important in patients with:

  • pre-existing chronic kidney disease;
  • diabetes;
  • hypertension;
  • a solitary kidney;
  • bilateral upper-tract tumours; or
  • conditions likely to affect future kidney function.

The decision between kidney-sparing treatment and radical nephroureterectomy therefore involves balancing two priorities:

adequate cancer control and preservation of renal function.

Cancer safety remains the priority, but in appropriately selected low-risk disease these objectives can often coexist.

When Should You See a Urologist?

Seek medical assessment if you develop:

  • visible blood in the urine;
  • persistent microscopic haematuria;
  • unexplained flank or loin pain;
  • recurrent unexplained urinary symptoms;
  • abnormal findings on kidney imaging; or
  • haematuria with a previous history of urothelial cancer.

Blood in the urine should not automatically be attributed to prostate enlargement, infection, kidney stones or blood-thinning medication without appropriate investigation.

The Bottom Line

Upper tract urothelial carcinoma is an uncommon cancer arising from the lining of the renal pelvis or ureter.

Blood in the urine is its most important warning sign.

Investigation commonly involves CT urography, cystoscopy, urine cytology and, when required, ureteroscopy with biopsy.

Treatment is increasingly tailored to the biological risk of the tumour.

Small, low-grade tumours may sometimes be managed with kidney-sparing ureteroscopic laser treatment or segmental surgery, while high-risk invasive cancers generally require radical nephroureterectomy with removal of the bladder cuff, sometimes combined with lymph-node surgery and systemic treatment.

Long-term surveillance is essential because urothelial cancer can recur elsewhere within the urinary tract, particularly the bladder.

The reassuring part is that when UTUC is detected while still superficial and localised, the likelihood of successful treatment can be very high.

A Note for Patients

Every upper tract urothelial tumour is different. Treatment depends upon the tumour’s location, size, grade, stage, number of lesions, kidney function and your general health.

Management should therefore be individualised following discussion with your urologist and, for higher-risk disease, a multidisciplinary uro-oncology team.

This information is intended for general patient education and should not replace individual medical advice, examination or treatment recommendations from your treating specialist.

The current 2026 EAU guideline specifically incorporates updated risk stratification, kidney-sparing management, bladder-cuff and lymph-node considerations, systemic therapy, and follow-up recommendations.

Small Renal Masses: When a Small Kidney Tumour Needs Watching, Treating or Removing

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Finding a small mass on the kidney can be unsettling, particularly when it appears unexpectedly on an ultrasound or CT scan performed for something completely unrelated.

The reassuring news is that small does not automatically mean dangerous, and a renal mass does not automatically mean kidney cancer. Even when a small renal mass is malignant, many grow slowly and have a low risk of spreading. This means that immediate surgery is not always necessary.

Modern management has therefore moved away from a simple philosophy of “there is a lump, so it must come out”. Instead, treatment is tailored to the size and appearance of the mass, its growth rate, kidney function, the patient’s age and general health, and individual preferences.

Options range from:

  • Active surveillance
  • Percutaneous biopsy
  • Minimally invasive ablation, including cryoablation and thermal techniques
  • Robotic partial nephrectomy
  • Occasionally, radical nephrectomy

The aim is straightforward: control the cancer when treatment is necessary while preserving as much normal kidney function as possible.

What Is a Small Renal Mass?

A small renal mass (SRM) generally refers to a kidney tumour measuring 4 cm or less, corresponding to a clinical T1a renal tumour when confined to the kidney.

Many are discovered incidentally during imaging performed for abdominal pain, gallstones, bowel problems, back pain or another unrelated condition. The kidney lesion is often an unexpected passenger on the scan.

Importantly, not every small renal mass is cancer.

Benign lesions include:

  • Oncocytoma
  • Angiomyolipoma
  • Some complex renal cysts
  • Other uncommon benign tumours

Among malignant masses, renal cell carcinoma is the most important diagnosis. However, many small renal cancers demonstrate relatively indolent behaviour. Published guideline data suggest that more than 20% of small renal masses may ultimately prove benign, while many malignant lesions within this size range have relatively favourable biology.

This creates an important clinical dilemma: we want to treat a potentially dangerous cancer, but we also want to avoid unnecessary treatment of a tumour that may never have caused harm.

Step One: Properly Characterising the Mass

An incidental renal mass generally requires appropriate imaging before deciding what to do.

This usually involves a:

  • Multiphasic contrast CT scan, or
  • MRI scan

These scans help determine:

  • Exact tumour size
  • Whether the lesion is solid or cystic
  • Whether it enhances with contrast
  • Its position within the kidney
  • Relationship to blood vessels and the collecting system
  • Whether there are concerning features suggesting malignancy
  • Whether there is any evidence of disease outside the kidney

High-quality contrast CT or MRI is recommended for the characterisation of a newly discovered small renal mass.

Blood tests will usually include kidney function, particularly serum creatinine and estimated glomerular filtration rate (eGFR).

What About Complex Kidney Cysts?

Not every suspicious renal lesion is a solid tumour.

Complex renal cysts are usually classified according to the Bosniak classification, which estimates the likelihood that a cystic lesion represents malignancy.

Some Bosniak III and selected predominantly cystic lesions can also be considered for surveillance, particularly when they are small or when the risks of treatment outweigh the anticipated benefits. Larger or increasingly complex lesions are more likely to require intervention.

Do We Need a Kidney Biopsy?

Sometimes.

A renal mass biopsy involves passing a needle through the skin into the tumour, usually under ultrasound or CT guidance, and obtaining small samples for examination by a pathologist.

Biopsy can be particularly useful when:

  • The diagnosis is uncertain
  • Active surveillance is being considered
  • The biopsy result could change management
  • Ablation is planned
  • Imaging suggests a tumour that may not require surgery
  • There is a possibility of metastatic disease or another unusual diagnosis

A biopsy is not automatically necessary for every small renal mass.

Possible complications include:

  • Pain
  • Bruising
  • Bleeding around the kidney
  • Rare significant haemorrhage
  • Non-diagnostic biopsy
  • Sampling error

The important question is not simply “Can we biopsy it?” but rather:

“Will knowing the biopsy result change what we do?”

Option 1: Active Surveillance

Active surveillance is increasingly recognised as a legitimate management strategy rather than simply “doing nothing.”

There is an important difference.

Doing nothing means ignoring the tumour.

Active surveillance means deliberately monitoring it and treating it if its behaviour changes.

For appropriately selected small renal masses, particularly those less than 2 cm, active surveillance can be an excellent initial strategy. The AUA notes very favourable cancer-specific and metastasis-free outcomes in published surveillance series of these very small tumours.

The overall risk of metastatic progression among carefully selected patients undergoing surveillance for small renal masses has been reported at approximately 1–2% or less in early follow-up series, although risk varies according to tumour and patient characteristics and increases with more aggressive biological behaviour.

Who May Be Suitable for Active Surveillance?

Surveillance may be particularly attractive for:

  • Tumours less than 2 cm
  • Small tumours with favourable imaging characteristics
  • Slowly growing lesions
  • Older patients
  • Patients with significant medical problems
  • Patients with impaired kidney function
  • Patients with a solitary kidney
  • Patients at increased anaesthetic or surgical risk
  • Patients who wish to avoid or delay intervention

For renal masses measuring 2–4 cm, both surveillance and definitive treatment may be reasonable depending upon individual circumstances.

What Does an Active Surveillance Protocol Look Like?

There is no single surveillance schedule suitable for every patient.

A commonly used approach is:

Baseline

Obtain good-quality CT or MRI imaging to accurately document:

  • Tumour size
  • Tumour characteristics
  • Location
  • Complexity

A renal mass biopsy may be considered when the result would influence management.

First follow-up

Repeat cross-sectional imaging is commonly performed approximately 3–6 months after entering surveillance to determine whether there is meaningful interval growth. This approach is specifically supported by AUA guidance.

Ongoing surveillance

If the lesion remains stable, imaging may then be performed approximately:

Every 6–12 months, depending upon the patient’s age, tumour characteristics, previous growth rate and overall health.

Ultrasound can sometimes reduce the number of CT scans required, provided that the lesion can be reliably visualised and measured. CT or MRI is preferred if there is uncertainty regarding growth or tumour characteristics.

The Canadian guideline notes that commonly used protocols involve abdominal imaging every 3–6 months during the first year and every 6–12 months thereafter if stable, although there is no universally agreed schedule.

When Do We Stop Watching and Start Treating?

This is perhaps the most important aspect of active surveillance.

Treatment may be recommended if there is:

  • Significant tumour growth
  • Increasing radiological complexity
  • Growth towards or beyond 4 cm
  • A consistent growth rate greater than approximately 5 mm per year
  • Concerning biopsy findings
  • Evidence of spread
  • Development of symptoms
  • A change in the patient’s health or treatment preference

Commonly recognised triggers include tumour growth beyond 4 cm or consecutive growth exceeding approximately 0.5 cm per year, although no single measurement should be considered in isolation.

A tumour that grows by a millimetre on one scan has not necessarily sounded the alarm bell. Small differences can occur simply because of how the scan or measurement was performed.

The trend matters more than a single measurement.

Risks and Disadvantages of Active Surveillance

The main advantages are avoiding or delaying unnecessary treatment and preserving kidney function.

Potential disadvantages include:

  • Anxiety associated with living with an untreated renal mass
  • Repeated scans
  • Radiation exposure from repeated CT imaging
  • Contrast exposure
  • Possibility of tumour growth
  • Small risk of metastatic progression
  • Possibility that treatment becomes technically more difficult if the tumour grows substantially

Active surveillance therefore works best when there is a clear follow-up plan rather than a vague agreement to “scan it again sometime.”

Option 2: Minimally Invasive Tumour Ablation

For selected small renal masses, it may be possible to destroy the tumour without surgically removing it.

This is known as renal tumour ablation.

The principal techniques include:

Cryoablation

Cryoablation uses extremely low temperatures to freeze and destroy tumour cells.

Radiofrequency Ablation

Radiofrequency ablation uses thermal energy to heat and destroy tumour tissue.

Microwave Ablation

Microwave energy can similarly produce controlled heating and destruction of tumour tissue.

These treatments can often be performed percutaneously, meaning probes are inserted through the skin under CT or ultrasound guidance without requiring conventional surgery.

Who Is Suitable for Renal Ablation?

Ablation may be considered for patients with:

  • A small renal tumour
  • A tumour in a technically accessible location
  • Significant medical comorbidities
  • Increased surgical or anaesthetic risk
  • Reduced kidney function
  • A solitary kidney
  • Previous kidney surgery
  • A strong preference for a less invasive treatment

Current European guidance particularly supports tumour ablation as an alternative for patients with small cT1 renal tumours who require treatment but are unfit for surgery, while emphasising that long-term comparative evidence against partial nephrectomy remains less robust.

Renal mass biopsy is generally recommended before percutaneous ablation.

Advantages of Ablation

Potential benefits include:

  • No large surgical incision
  • Shorter hospital stay
  • Faster recovery
  • Less postoperative discomfort
  • Preservation of kidney tissue
  • Potential suitability for patients who are poor surgical candidates
  • Ability to repeat treatment in selected cases

Risks and Complications of Ablation

Possible complications include:

  • Bleeding
  • Haematoma
  • Infection
  • Pain
  • Damage to nearby organs
  • Injury to the collecting system
  • Urine leakage
  • Thermal injury to surrounding structures
  • Incomplete treatment
  • Persistent viable tumour
  • Local tumour recurrence
  • Need for repeat ablation
  • Need for subsequent surgery

Tumour size matters. European guidance advises against routinely using radiofrequency ablation for tumours larger than approximately 3 cm and cryoablation for tumours larger than approximately 4 cm, because recurrence becomes more concerning as tumour size increases.

Long-term oncological evidence for ablation is also less mature than the evidence supporting surgical excision, and local recurrence appears somewhat more frequent than following partial nephrectomy.

Option 3: Robotic Partial Nephrectomy

When definitive surgical treatment is appropriate, the modern objective is usually:

Remove the tumour, not the entire kidney.

A partial nephrectomy removes the renal tumour together with an appropriate margin while leaving the remaining healthy kidney intact.

For suitable T1a renal masses, partial nephrectomy is generally preferred over removing the whole kidney because it provides excellent cancer control while preserving more functioning renal tissue.

Increasingly, this operation is performed using robotic-assisted laparoscopic surgery.

What Happens During Robotic Partial Nephrectomy?

Several small incisions are made in the abdomen.

Using robotic instruments, the surgeon:

  1. Identifies the kidney and renal tumour.
  2. Carefully defines the tumour margins.
  3. May temporarily control blood flow to the kidney.
  4. Removes the tumour while preserving as much healthy kidney as possible.
  5. Repairs any opening into the collecting system if necessary.
  6. Controls bleeding.
  7. Reconstructs the remaining kidney.

The removed tumour is then sent to pathology, providing definitive information regarding:

  • Whether the tumour is benign or malignant
  • Type of renal tumour
  • Tumour grade
  • Exact size
  • Surgical margin status

This pathological information is one of the major advantages of surgical excision.

Who Should Consider Robotic Partial Nephrectomy?

Surgery may be preferred for:

  • Young and otherwise healthy patients
  • Enlarging tumours
  • Tumours approaching or exceeding 4 cm
  • Tumours with concerning imaging characteristics
  • Aggressive findings on biopsy
  • Patients with a long life expectancy
  • Tumours unsuitable for ablation
  • Patients who prefer definitive removal

Partial nephrectomy is particularly valuable when preserving kidney function is important, including patients with:

  • Chronic kidney disease
  • A solitary functioning kidney
  • Bilateral renal tumours
  • Conditions that may threaten future kidney function

Complications of Robotic Partial Nephrectomy

Although robotic surgery is minimally invasive, it remains a significant operation.

Potential complications include:

  • Bleeding
  • Blood transfusion
  • Infection
  • Urinary tract infection
  • Injury to surrounding organs
  • Urine leakage from the kidney
  • Damage to the renal collecting system
  • Temporary reduction in kidney function
  • Permanent loss of some kidney function
  • Blood clots
  • Anaesthetic complications
  • Hernia
  • Positive surgical margin
  • Conversion to open surgery
  • Conversion to radical nephrectomy
  • Rare loss of the kidney
  • Rare cardiovascular or other serious complications

One particular delayed complication is a renal artery pseudoaneurysm, which may cause bleeding several days or even weeks after surgery and occasionally requires radiological embolisation.

Fortunately, most patients undergoing uncomplicated robotic partial nephrectomy recover relatively quickly and retain excellent kidney function.

Does the Whole Kidney Ever Need to Be Removed?

Yes, but for a straightforward small renal mass this is increasingly avoided when partial nephrectomy is technically and oncologically appropriate.

A radical nephrectomy removes the entire kidney.

It may still be necessary when:

  • The tumour is very large
  • The tumour occupies much of the kidney
  • Tumour location makes partial nephrectomy unsafe
  • There is extensive involvement of major renal blood vessels
  • The remaining kidney tissue would provide little useful function
  • Cancer control would be compromised by attempting partial nephrectomy

The decision is therefore not simply based upon tumour diameter. Tumour anatomy matters enormously.

What Happens After Treatment?

Treating the tumour does not mean that follow-up disappears.

Continued surveillance is important following both ablation and surgery.

The intensity of follow-up depends upon:

  • Final pathology
  • Tumour stage
  • Tumour grade
  • Surgical margins
  • Treatment performed
  • Kidney function
  • Patient age and general health
  • Risk of recurrence

Follow-Up After Partial Nephrectomy

Patients will generally undergo periodic assessment including:

  • Blood pressure
  • Kidney function
  • Serum creatinine and eGFR
  • Urinalysis when indicated
  • Abdominal imaging
  • Chest imaging when clinically appropriate

CT, MRI or ultrasound may be used depending upon the patient’s recurrence risk and kidney function.

Higher-grade or higher-stage cancers generally require more intensive surveillance than a small, completely excised low-grade tumour.

Long-term follow-up is important because renal cell carcinoma can occasionally recur many years after apparently successful treatment.

Follow-Up After Ablation

Imaging is particularly important after tumour ablation because the tumour remains physically present even though the tissue has been destroyed.

Follow-up CT or MRI is therefore used to assess whether there is any persistent or recurrent contrast enhancement, which may indicate viable tumour.

Patients commonly require imaging relatively early after treatment followed by continued surveillance over subsequent years.

If residual tumour is identified, options may include:

  • Repeat ablation
  • Partial nephrectomy
  • Other surgical treatment
  • Continued surveillance in selected circumstances

And What About the Other Kidney?

Follow-up is not only about looking for recurrence.

Kidney health matters.

Patients who have undergone treatment for a renal tumour should pay attention to:

  • Blood pressure
  • Diabetes control
  • Smoking cessation
  • Healthy body weight
  • Kidney function
  • Avoidance of unnecessary kidney-toxic medications
  • Cardiovascular health

Preserving functioning kidney tissue is one reason partial nephrectomy and appropriately selected minimally invasive approaches have become so important.

The Bottom Line

A small renal mass is not automatically an emergency and not automatically a cancer requiring immediate surgery.

Modern management is increasingly personalised.

For one patient, the safest option may be:

Watch it carefully.

For another:

Biopsy it first.

For another:

Ablate it.

And for another:

Remove the tumour robotically while preserving the kidney.

The decision depends upon the tumour’s size, location, appearance, growth and biology, balanced against the patient’s age, kidney function, general health and personal preferences.

Perhaps the most important message is this:

Small renal masses deserve respect, but not necessarily panic.

Active surveillance can be an active treatment strategy in itself. Minimally invasive ablation can provide an alternative for selected patients, particularly those who are less suitable for surgery. And when definitive surgery is appropriate, robotic partial nephrectomy allows many tumours to be removed while preserving the majority of the kidney.

Whichever strategy is chosen, the story does not finish on treatment day. Continued imaging and kidney-function surveillance remain an important part of long-term care.

This information is intended for general patient education and should not replace individual assessment by a urologist. Management of a renal mass should be personalised according to imaging findings, kidney function, medical history, tumour characteristics and patient preferences.

Please note, I no longer do surgery for renal cancer but will continue with your surveillance as long as it does not require surgery. I will then refer you to a Urologist interested in doing these procedures. I can however manage this for you where focal therapy is done by the intervention radiologist.

Renal angiomyolipoma (AML): when to watch, when to treat and when to seek urgent help

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An angiomyolipoma, usually shortened to AML, is a growth in the kidney made up of blood vessels, muscle-like tissue and fat. Most are found by chance on a scan and never cause trouble. The main concern is that some AMLs can bleed, occasionally quite severely. The right plan depends on the diagnosis, the growth’s features and your circumstances, not its diameter alone. [1,2]

In this article, “AML” means angiomyolipoma, not acute myeloid leukaemia.

Is an AML cancer?

A classic renal AML is generally a benign tumour. Most occur on their own (sporadic AML). Some occur with tuberous sclerosis complex (TSC) or, less commonly, lymphangioleiomyomatosis (LAM); these can be multiple, affect both kidneys and require a different surveillance and treatment approach. A rare epithelioid AML can behave aggressively and needs specialist assessment. Not every solid renal mass presumed to be an AML can be confidently identified on a scan, particularly when little visible fat is present. [1,3,4]

What symptoms can it cause?

Many AMLs have no symptoms. Possible symptoms include aching or pain in the side, visible blood in the urine, or, less commonly, a palpable swelling. A sudden bleed into or around the kidney may cause abrupt, severe flank or abdominal pain, sometimes with dizziness, fainting, weakness or a racing heart. Blood in the urine and flank pain can also have other causes, including stones or cancer, so they should be assessed rather than attributed automatically to a known AML. [1–3]

Emergency warning: If you develop sudden severe side or abdominal pain, especially with faintness, collapse, a racing heart or visible bleeding, call 000 in Australia or attend an emergency department immediately. A bleeding AML can cause major blood loss even when blood is not visible in the urine. Do not wait for a routine appointment. [1,3]

How is it diagnosed?

An AML may first appear on an ultrasound performed for another reason. CT or MRI helps confirm whether it contains fat and assess its size, location, blood vessels and any evidence of bleeding. Contrast-enhanced imaging may be needed for an indeterminate lesion or procedural planning, with the choice adapted to kidney function, pregnancy and other factors. A classic fat-rich AML is often diagnosed on imaging alone. A fat-poor AML may resemble kidney cancer; specialist review, further imaging or a biopsy may be appropriate if the result would change management. Biopsy has limitations and is chosen case by case. [1,3,4]

The assessment may also include blood pressure, kidney function and a blood count if bleeding is suspected. Multiple or bilateral AMLs, especially in a younger person, should prompt consideration of TSC or LAM and appropriate specialist input. [3,5]

Is there a critical size that must be treated?

There is no single diameter at which every AML must be removed. The traditional rule to treat an AML once it reaches 4 cm is no longer considered an automatic trigger. The European Association of Urology (EAU) states that the relationship between size and bleeding risk is uncertain and that no universal intervention threshold exists. Some larger AMLs can still be watched safely; a smaller one may need treatment if it bleeds or causes persistent symptoms. [1,2]

Size remains one part of the discussion. The team may also consider growth, vascular features or aneurysms seen on imaging, prior bleeding, pain, kidney function, pregnancy plans, blood-thinning medicines and access to urgent care. An aneurysm measurement such as 5 mm has been proposed as a risk marker, but recent evidence questions how reliably it predicts bleeding on its own. These findings guide an individual discussion; they do not supply a stand-alone rule. [1,3,6]

Management options

Active surveillance

For a confidently diagnosed, symptom-free AML, monitoring is often appropriate. It avoids exposing people with stable lesions to procedure risks. A surveillance plan records the starting size and imaging characteristics, checks for new symptoms and uses ultrasound, MRI or CT when appropriate to look for change. There is no single imaging interval suitable for all sporadic AMLs. A small, stable lesion may need little or no ongoing imaging after specialist review; a larger or changing lesion usually needs closer follow-up. Agree on the next scan, who will review it and what changes should prompt earlier contact. [1–3]

Selective arterial embolisation

An interventional radiologist passes a catheter into the blood vessels feeding the AML and blocks selected branches. Embolisation can control active bleeding and can be considered in advance for selected higher-risk or symptomatic tumours, while preserving kidney tissue. Pain, fever and nausea can occur afterwards; infection, non-target embolisation and repeat treatment are possible. In the EAU systematic review, around 30% of embolised cases required a further intervention, although individual outcomes vary. [1,2]

Kidney-sparing surgery

A partial nephrectomy removes the AML while aiming to preserve the rest of the kidney. Open, laparoscopic or robotic approaches may be considered depending on anatomy and surgical expertise. Surgery may be useful when imaging is uncertain, symptoms persist, embolisation is unsuitable or a definitive removal is preferred. It carries anaesthetic, bleeding, urine leak and kidney-function risks. Removal of the whole kidney is generally reserved for situations where kidney-sparing care is not feasible, especially in an emergency. [1–3]

Ablation and medicines

Thermal ablation is used less often for AML, and the evidence is more limited than for surveillance, embolisation and surgery. For TSC-associated AML, specialist teams may use an mTOR inhibitor such as everolimus for an asymptomatic but growing lesion over 3 cm when treatment is appropriate. This TSC recommendation should not be applied automatically to an isolated sporadic AML. Medicines require monitoring for adverse effects and interactions. [1,2,5]

What happens if an AML bleeds?

In hospital, the immediate priorities are resuscitation, blood tests and imaging to locate the bleed. Treatment may include intravenous fluids, blood transfusion and urgent selective arterial embolisation to stop the bleeding. Surgery is considered if embolisation is unavailable, unsuccessful or otherwise unsuitable. After recovery, follow-up checks the AML, remaining kidney function and whether further treatment is needed. [1,3]

How is surveillance different with tuberous sclerosis?

TSC-related AMLs require a coordinated long-term plan because lesions may occur in both kidneys and kidney function needs protection over a lifetime. The 2021 international TSC recommendations advise abdominal MRI every 1–3 years, with blood pressure, kidney function and urine protein checked at least yearly; the interval is tailored to individual risk. Growing AMLs greater than 3 cm may merit first-line mTOR treatment when intervention is indicated, while acute bleeding is generally managed with embolisation. A TSC specialist team can help balance treatment against the need to preserve kidney tissue. [5]

Questions to bring to your appointment

  • Is the imaging diagnosis of a classic AML secure, or is more investigation needed?
  • What are its size, growth pattern and vascular features?
  • What is my personal risk of bleeding, and how does kidney function affect my options?
  • If we monitor it, when is my next scan and what result would change the plan?
  • If treatment is recommended, why is embolisation, surgery or another option best for me?

This article provides general information and does not replace individual assessment or advice.

References

  1. European Association of Urology. EAU Guidelines on Renal Cell Carcinoma, section on other renal tumours and AML. Accessed September 2026.
  2. Fernández-Pello S, et al. Management of sporadic renal angiomyolipomas: a systematic review to guide EAU recommendations. European Urology Oncology. 2020;3:57–72. doi:10.1016/j.euo.2019.04.005.
  3. Guo Y, et al. Canadian Urological Association best practice report: Diagnosis and management of sporadic angiomyolipomas. Canadian Urological Association Journal. 2020;14–E536. doi:10.5489/cuaj.6942.
  4. Wilson MP, et al. Diagnostic performance of MRI in detection of renal lipid-poor angiomyolipomas: systematic review and meta-analysis. Radiology. 2020;296:511–520.
  5. Northrup H, et al. Updated international TSC diagnostic criteria and surveillance and management recommendations. Pediatric Neurology. 2021;123:50–66. See also Tuberous Sclerosis Australia: Kidneys.
  6. Swärd J, et al. Renal angiomyolipoma: investigating radiological signs indicative of bleeding risk. Insights into Imaging. 2025.

Robotic Assisted Partial Nephrectomy

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Indications:

  • Small renal cancers
  • Exophytic
  • Not involving the collecting system
  • Single kidney
  • Fit for surgery
  • Nephron-sparing

No longer offered in my practice and will be referred a Urologist who does.