Renal Angiomyolipoma (AML)

What is a renal angiomyolipoma?

Renal angiomyolipoma is a benign tumor of the kidney. It consists of blood vessels, muscle and fat. Angiomyolipoma are seen in about 0.13% of the general population. They are most commonly found on imaging done for other causes. Angiomyolipomas are more common in women than men. They are most commonly seen in people age 40 to 60. Angiomyolipoma can a randomly or can be part of a genetic syndrome, such as tuberous sclerosis complex. When small, less than four centimeters (1.6 inches), an angiomyolipoma can be monitored. Monitoring is typically done with periodic imaging such as ultrasound.

When should a renal angiomyolipoma be treated?

When an angiomyolipoma approaches four centimeters there is a risk of bleeding. Sudden unexpected bleeding in the kidney without trauma is called Wunderlich syndrome. Sometimes the bleed can cause back and/or abdominal pain. Sometimes the bleed can be serious and require hospital admission and blood transfusion.

Once an angiomyolipoma reaches four centimeters, a procedure is recommended to shrink it. This procedure is called renal embolization. This is done by an interventional radiologist. A catheter is placed into a blood vessel, typically in the groin. Material such as coils or foam is released into the blood vessel feeding the angiomyolipoma. This causes the angiomyolipoma to shrink.

If the interventional radiologist cannot find the blood vessel, or if the angiomyolipoma doesn’t shrink or regrows after embolization, surgery may be needed. This is typically removal of the part of the kidney with the angiomyolipoma. This is called partial nephrectomy. Partial nephrectomy can be performed with open, laparoscopic or robotic surgery.

Consideration for women of childbearing age

In women of childbearing age, it may be advisable to treat an angiomyoma at less than four centimeters. Pregnancy can increase the risk of kidney bleed. Therefore, embolization to shrink the angiomyolipoma maybe recommended at smaller sizes for women of childbearing age, especially if the woman is thinking about pregnancy.

Renal Angiomyolipoma Embolization
Renal Angiomyolipoma Post-procedure Instructions