Renal Angiomyolipoma

What is renal angiomyolipoma?

A renal angiomyolipoma (AML) is a type of tumor in your kidney. Almost all are benign (noncancerous), but they can hemorrhage, which can be life-threatening.

A tumor occurs when cells grow and divide more than they should. A renal angiomyolipoma is made of blood vessels, muscle cells and fat.

How common is renal angiomyolipoma?

Angiomyolipomas are the most common kind of benign renal tumor, affecting about 0.2% to 0.6% of people, mostly women over 50.

Is renal angiomyolipoma associated with other problems?

Renal AMLs are often associated with:

• Lymphangioleiomyomatosis.
• Neurofibromatosis type 1.
• Tuberous sclerosis complex.
• von Hippel-Lindau disease.

What causes renal angiomyolipoma?

Renal angiomyolipoma is caused by a genetic mutation to the TSC1 or TSC2 gene (tumor suppressor genes). They are responsible for producing tuberin, a protein that helps control cells’ growth and size. When the TSC genes mutate or change, it affects the production of tuberin, and cells may grow out of control.

What are the symptoms of renal angiomyolipoma?

Most people with renal AML don’t have any symptoms. Instead, the condition is usually discovered by accident when a person has kidney tests for another reason.

Less often, renal angiomyolipoma is discovered because of retroperitoneal hemorrhage. This occurs when part of the tumor ruptures (breaks) and blood enters the space in your abdomen (belly). Retroperitoneal bleeding is a serious, potentially life-threatening problem.

Rare symptoms include:

• Anemia (not enough healthy red blood cells).
• Discomfort or pain in the abdomen, back and sides.
• Hematuria (blood or blood cells in your pee).
• High blood pressure (hypertension).
• Kidney failure.
• A lump you can feel.
• Urinary tract infection.

How is renal angiomyolipoma diagnosed?

Renal angiomyolipomas are often diagnosed accidentally during tests to look at your kidneys for other reasons. These tumors are typically found during screening in people with tuberous sclerosis or another condition associated with AML.

A healthcare provider can diagnose a renal AML based on imaging tests that take pictures inside your abdomen:

• CT scan.
• MRI.
• Ultrasound.

In most cases, an imaging test is the only test needed for diagnosis. Renal angiomyolipomas are often golden yellow because of their fat content. They can range in size from 1 to 20 cm (with an average of 9 cm).

Sometimes, if your healthcare team can’t tell whether a tumor is benign or cancerous, they may order a kidney biopsy. The surgical procedure removes a small part of the tumor. Then an expert looks at the cells under a microscope to determine whether they are cancerous.

How is renal angiomyolipoma treated?

Renal angiomyolipoma treatment varies widely, from active surveillance to medication to surgical removal.

If a renal angiomyolipoma is small and isn’t causing any symptoms, your healthcare provider may recommend active surveillance. With this approach, also called “watch and wait,” you won’t have any treatment. You’ll have regular tests to monitor the tumor for any changes.

The tumor may also respond to a type of medication called mTOR inhibitors. These are a type of targeted therapy that addresses the genetic mutation. They can stop the tumor from growing or shrink it.

Your healthcare provider may recommend surgery if:

• AML causes symptoms.
• Mass grows to 4 cm or larger.
• The tumor might be cancerous.
• You are a woman of child-bearing age (to prevent potential damage to reproductive organs).
• You have limited access to follow-up care or emergency services, which you would need for hemorrhage.

Surgical treatment may involve:

• Embolization, which blocks the blood supply to the tumor and is a useful tool in renal AML bleeding emergencies.
• Nephrectomy, which involves removing part or all of your affected kidney.
• Radiofrequency ablation, which uses heat to destroy abnormal tissue.
• Nephron-sparing surgery or partial nephrectomy.

How can I reduce my risk of renal AML?

There are no strategies to prevent the genetic mutations that lead to renal angiomyolipoma.

But if you have certain other medical conditions, you should have imaging tests regularly to catch AML early:

• Lymphangioleiomyomatosis.
• Neurofibromatosis type 1.
• Tuberous sclerosis complex.
• von Hippel-Lindau disease.

What can I expect if I have this condition?

Renal angiomyolipomas are usually small, and they rarely become a major problem. But a very small proportion can become malignant (cancerous) or cause serious bleeding. Renal AMLs should be monitored carefully. Your healthcare provider will talk to you about how often you should have imaging tests.

Even after treatment, AML can recur (come back). You should follow up with your healthcare team for regular testing.

When should I seek medical attention?

If you’ve been diagnosed with a renal AML or one of the conditions associated with AML, be aware of the signs of retroperitoneal bleeding. Seek medical attention immediately if you experience:

• Blood in your urine.
• Pain in your belly or upper legs that won’t go away.
• Signs of shock, including confusion, rapid heart rate, dizziness, shallow breathing and pale skin.

A note from Cleveland Clinic

Renal angiomyolipoma (AML) is a benign (noncancerous) tumor in your kidney. It’s often found accidentally during testing or screening for another condition. If you’ve been diagnosed with a renal AML, talk to your healthcare provider about treatment options. It should be monitored regularly to prevent bleeding, which can be life-threatening.