Renal angiomyolipoma

> 4 cm consider removal even if asymptomatic given increased risk of hemorrhage
Although a homogeneous, highly hyperechoic mass is very suggestive of AML, approximately 10% of RCCs can mimic this appearance
One distinguishing feature seen in 20-30% of AMLs is some degree of acoustic shadowing, which, in the absence of calcification, is extremely rare in RCC
- Shadowing due to attenuation by mixture of fatty and soft-tissue elements
Cystic components rare in AML but more common in RCC

Hyperechoic renal masses that show no partial shadowing require further evaluation

≥ 1 cm you should be able to detect fat on CT or MRI (may be harder to discern if any smaller due to volume averaging)
If no fat on a lesion ≥ 1 cm on CT/MRI, then highly suspicious for RCC
< 1cm it is reasonable to monitor with periodic surveillance ultrasounds

RCC (as above)
Deep cortical scars
- In most cases scars are filled with perinephric fat
Cysts almost completely filled with crystals
- Will usually see color Doppler twinkle artifact