Angiomyolipoma Of The Kidney
Angiomyolipoma (AML) of the kidney is a benign tumor made up of fat, blood vessels, and smooth muscle tissue. Most AMLs occur sporadically and are discovered incidentally during imaging, but some are associated with genetic conditions such as tuberous sclerosis. Small AMLs typically cause no symptoms, while larger ones may lead to flank pain, bleeding, or a palpable mass.
What is it?
Angiomyolipoma is a benign kidney tumor composed of a mix of fat, muscle, and blood vessels. Its fat content usually makes it easy to recognize on imaging, particularly CT or MRI. Most AMLs are small and harmless, but tumors larger than 4 cm have a higher risk of bleeding because of fragile blood vessels within the mass. Rare variants with minimal fat can mimic other kidney lesions, requiring more detailed imaging.
Imaging helps confirm the diagnosis by identifying the characteristic fat within the lesion. MRI is especially useful for fat-poor AMLs, while CT is excellent for detecting even small amounts of fat. Radiologists also assess size, growth, and any signs of bleeding or aneurysms that may require treatment.
Important to Know
Most AMLs do not require treatment and remain stable for years. However, larger tumors may bleed spontaneously, causing sudden flank pain or low blood pressure, which is a medical emergency. People with tuberous sclerosis often have multiple AMLs and require periodic monitoring.
Red flag symptoms include sudden severe flank pain, dizziness, fainting, or blood in the urine—these may indicate bleeding and require urgent care. Treatment options include minimally invasive procedures like embolization, medication (such as mTOR inhibitors), or surgery for complex cases. Follow-up imaging is typically recommended to monitor size and progression.