kidneys
what are angiomyolipomas or AMLs?
Renal angiomyolipomas (AMLs) are benign kidney tumors composed of blood vessels, smooth muscle cells, and fat. They are the most common type of benign renal tumor and are often discovered incidentally during imaging for other conditions. While most AMLs are small and asymptomatic, larger tumors may cause complications due to their tendency to bleed, particularly when they exceed 4 cm in size.
AMLs are frequently associated with tuberous sclerosis complex (TSC), a genetic disorder that causes the growth of benign tumors in various organs. However, they can also occur sporadically in individuals without TSC. The risk of complications, such as haemorrhage, increases with tumor size, and treatment decisions are typically based on the size and symptoms of the AML, with options ranging from monitoring to minimally invasive interventions like embolization or surgery.
the symptoms
The majority of AMLs are asymptomatic and discovered incidentally
Asymptomatic in many cases:
Small AMLs, particularly those under 4 cm in size, are often asymptomatic and discovered incidentally during imaging for other conditions.
Most patients with small AMLs do not experience any noticeable symptoms.
Pain and discomfort:
Larger AMLs can cause flank pain or a feeling of fullness in the abdomen due to their size and pressure on surrounding structures.
Back pain is also a common symptom as the tumor grows.
Some patients may report tenderness or discomfort in the abdominal or kidney region.
Bleeding complications:
The blood vessels within AMLs are fragile and can rupture, leading to hemorrhage.
This can cause sudden, severe pain in the flank or abdomen, often accompanied by nausea and vomiting.
Hematuria (blood in the urine) may occur if there is bleeding into the urinary tract. In rare cases, massive hemorrhage can cause hypovolemic shock.
Diagnosis of AMLs
Incidental discovery:
Most AMLs are found during routine imaging such as ultrasound, CT scan, or MRI when investigating unrelated conditions.
These imaging tests can detect the presence of fat within the tumor, a key characteristic of AMLs that helps distinguish them from other kidney masses.
Ultrasound:
An initial renal ultrasound may identify an AML as a hyperechoic (bright) lesion in the kidney due to its fat content.
Ultrasound is often the first-line imaging tool used in patients with kidney-related symptoms.
CT and MRI:
CT scans are commonly used to confirm the diagnosis, as they can provide detailed images of the tumor, including the amount of fat, which is a hallmark of AMLs.
MRI is particularly useful in distinguishing AMLs from other types of renal tumors when there is uncertainty.
Both imaging techniques help assess the size and extent of the tumor, guiding treatment decisions.
Kidney biopsy in selected cases:
While imaging is usually sufficient for diagnosing AMLs due to their characteristic fat content, a kidney biopsy may be performed in certain cases where the diagnosis is unclear.
Biopsy can help distinguish AMLs from other renal masses, especially if the tumor lacks visible fat on imaging or if malignancy is suspected.
This approach is particularly useful in cases of fat-poor AMLs, which can be more challenging to differentiate from other kidney tumors through imaging alone.
Risk of Complications and Surveillance
Tumor size and bleeding risk:
The risk of hemorrhage increases as the size of the AML exceeds 4 cm, prompting closer monitoring or treatment.
Regular imaging surveillance is often recommended for patients with AMLs, especially if the tumor is growing or symptomatic.
Family history and genetic conditions:
For patients with tuberous sclerosis complex (TSC) or a family history of AMLs, a more detailed evaluation may be required to monitor for multiple or larger tumors.
Genetic testing and counseling may also be part of the diagnostic process for those with
What happens after referral
For non-urgent cases ,after receiving your referral, our practice nurse will triage your case, and you'll be quickly contacted for a brief overview of your condition. After your visit, you can schedule several diagnostic tests, urine analysis, ultrasound, and CT scans to help you evaluate. At your appointment, A/Prof Homi Zargar will engage with you, conduct a thorough assessment, and review the gathered information. A personalized care plan addressing your symptoms will be devised, ensuring all your questions are addressed.
Treatment options
Management of AMLs depends on factors such as tumor size, symptoms, and the risk of complications, with an emphasis on balancing effective treatment and preserving kidney function.
Surveillance:
For small, asymptomatic AMLs (typically under 4 cm), active surveillance with regular imaging is recommended to monitor for growth or the development of symptoms.
This approach is appropriate when the risk of complications, such as bleeding, is low. However, in women of childbearing age who plan to become pregnant, careful consideration is necessary, as AMLs can grow during pregnancy under the influence of hormones, increasing the risk of hemorrhage and other complications.
Close monitoring during pregnancy or planning for proactive treatment beforehand is essential to manage the potential risks.
Medical therapy for tuberous sclerosis complex (TSC):
In patients with TSC, mTOR inhibitors such as everolimus can be used to shrink the tumors and prevent complications.
This therapy is particularly beneficial for managing multiple or large AMLs and can delay or avoid the need for surgery.
Embolization:
Selective arterial embolization is used for larger AMLs, especially those with prominent blood vessels that are at risk of rupture. The procedure cuts off blood flow to the tumour, causing it to shrink and reducing the likelihood of bleeding.
However, ongoing imaging is required post-embolization, as the procedure may need to be repeated if the tumour revascularizes or grows again.
Partial nephrectomy:
An 18 cm AML was treated with nephron sparing surgery.
Robotic partial nephrectomy is increasingly used to remove AMLs while preserving kidney function, especially for larger tumours, as experience with the technique grows.
This surgery is particularly advantageous as it avoids the need for ongoing imaging and surveillance, unlike embolization, by definitively removing the tumour.
A/Prof Homi Zargar, a recognized expert in robotic surgery, has extensive experience performing robotic partial nephrectomies, even in challenging cases with larger AMLs. His expertise ensures the safe removal of the tumor while minimizing damage to healthy kidney tissue, offering patients excellent outcomes.
Radical nephrectomy:
In rare cases, a radical nephrectomy (removal of the entire kidney) may be necessary, typically for very large or complex tumors where kidney-sparing surgery is not feasible.
However, with the increasing success of robotic partial nephrectomy, the need for radical nephrectomy has significantly diminished, allowing for more kidney preservation in modern treatment approaches.
Our expertise in robotic partial nephrectomy offers an advanced treatment option for patients with larger AMLs, emphasizing kidney preservation while reducing the need for prolonged monitoring or repeated procedures.