Diagnostic Ultrasound - Abdomen and Pelvis

Renal Angiomyolipoma
Diagnoses: Urinary Tract
IMAGING
• Discrete intrarenal mass containing macroscopic fat
• Few mm to very large
• Triphasic angiomyolipoma (AML) histopathology: Varying
amounts of dysmorphic blood vessels, smooth muscle, and
mature adipose tissue; can be classified radiologically into
"classic" and "fat-poor" subtypes
• Classic AML: Contains fat measuring< -10 HU on NECT
• Fat-poor subtype ("AML with minimal fat"): Insufficient
amount of fat to be detected by conventional CT or MR
imaging
TOP DIFFERENTIAL DIAGNOSES
• Renal cell carcinoma
• After acute hemorrhage, RCC or AML may be
indistinguishable if no fat is detected
• Wilms tumor
• Renal oncocytoma
• Deep cortical scar
KEY FACTS
• Cortical milk of calcium cyst (MCC)
CLINICAL ISSUES
• Most common benign solid renal neoplasm
• Majority detected as incidental finding on imagingor during
screening of tuberous sclerosis
• 80% sporadic, prevalence 0.2%, 4th-6th decades; usually
unilateral and solitary
• Sporadic form more common in females than males (F:M =
3:1)
• 20% associated with tuberous sclerosis complex (TSC);
mean age younger; 55-75% of patients with TSC will have
AML by 3rd decade; any subtype of AML, multiple and
bilateral
• Tend to grow faster when > 4 cm
• Size > 4 cm or aneurysm size > 5 mm found to predict
bleeding
• AML associated with TSC more likely to need some form of
treatment
(Left) Graphic shows a
vascular renal mass containing
predominantly adipose ſt
components. Note the
tortuous feeding artery
arising from the main renal
artery. (Right) Transverse US
shows a small, wellmarginated,
hyperechoic mass
characteristic of
angiomyolipoma (AML). Note
the similar appearance to the
renal sinus fat ſt.
(Left) Corresponding
transverse color Doppler US
shows no significant color
flow in the small AML .
(Right) Axial CECT in delayed
phase shows an asymptomatic
classic fat-containing AML ſt
in the mid left kidney. Liver
cysts are noted
incidentally.
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