Renal Angiomyolipomas

What are Renal Angiomyolipomas?

Renal angiomyolipomas (AMLs) are benign tumors usually found in the kidneys. They are composed of smooth muscle, fat and blood vessels. AMLs can be diagnosed with radiographic imaging, such as computerized tomography (CT) or magnetic resonance imaging (MRI) scans.

Renal AMLs often cause no symptoms, and most are small and well-circumscribed and may only be detected incidentally. However, in some cases, AMLs can be large, particularly in patients with tuberous sclerosis, a genetic disorder characterized by multiorgan abnormalities. The larger tumors can be associated with abdominal discomfort, hematuria (blood in the urine) or can cause pain or even renal failure.

Causes of Renal Angiomyolipomas

In many cases, the cause of renal AMLs is unknown. In some cases, they can be linked to an inherited disorder called tuberous sclerosis. Tuberous sclerosis is caused by mutations in two genes, one called TSC1 and one called TSC2. People with these genes can develop many abnormal growths called tuberous sclerosis complex (TSC). In addition, some genetic conditions, such as Birt-Hogg-Dube syndrome, may be associated with the development of AMLs.

Symptoms of Renal Angiomyolipomas

Many AMLs are small and cause no symptoms, but they can sometimes become large and cause pain, blood in the urine, or even renal failure. A doctor may suspect an AML if a patient has any of the following symptoms:

  • Pain in the side, back, or abdomen
  • Blood in the urine (hematuria)
  • High blood pressure
  • Lumps in the abdomen or other areas
  • Abnormalities on imaging, such as CT scans or MRI

Treatment of Renal Angiomyolipomas

The treatment of AMLs depends on the size and location of the tumor.Small AMLs may not require any treatment, while large AMLs may need to be surgically removed. Some AMLs that cannot be surgically removed may be treated with medications such as sirolimus, which has been shown to reduce tumor size and improve symptoms. In some cases, embolization (the insertion of a wire into a blood vessel to block the flow of blood to the tumor) may also be used to reduce the size of an AML.