What it means
The name lists what it contains: blood vessels (angio), muscle (myo) and fat (lipoma). It grows in the kidney and is not cancer. The fat is the key to diagnosis. On CT, fat has a typical negative density value in Hounsfield units. On ultrasound it looks very bright, but so do some other lumps, so CT or MRI often confirms the fat. A few contain too little fat to see and are harder to tell apart.
When it matters
Most angiomyolipomas are found by chance and never cause problems. Small ones are often left alone or watched with occasional scans. Larger ones, often over about 4 cm, or ones with bulging blood vessels have a higher risk of bleeding. Your doctor may then suggest a treatment to shrink or remove them. Several angiomyolipomas in both kidneys can point to a genetic condition called tuberous sclerosis complex.
Questions to ask your doctor
- Does the lesion clearly contain fat, or is another test needed?
- How big is it, and how often should it be checked?
- Is there any sign of bleeding or of bulging blood vessels in it?
