Renal Angiomyolipoma (AML)




Figure 1a: Ultrasound image of a kidney showing a solid hyper-echoic rounded mass in the cortex of the renal parenchyma.

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Figure 1b: Annotated ultrasound of the same kidney with the solid hyper-echoic mass.

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Renal angiomyolipomas (AML) are a benign renal neoplasm that are composed of vascular (angio), smooth muscle (myo) and fat elements (lipo). The composition can be variable in terms of the proportion of each of these elements.


Typically an incidental finding, the greatest concern is of spontaneous haemorrhage, particularly those measuring more than 4cm.  For this reason AMLís are often followed up for size monitoring and if they exceed 4cm the risk-benefit for surgical removal or endovascular embolization is such that the lesion is usually treated.


On ultrasound AMLís are cortical based lesions (Figure 1), which are typically hyperechoiec (like the renal sinus fat).  No posterior acoustic shadowing is evident and the lesions are usually well circumscribed (Figure 2).


CT will confirm the presence of fat, as can MRI with fat suppressed sequences or in and out of phase which demonstrate signal drop out from the presence of intra-lesional fat.


Figure 2a: Ultrasound of the same kidney showing absence of posterior acoustic shadowing.

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Figure 2b: Annotated ultrasound of the same kidney showing absence of posterior acoustic shadowing. 

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Images and text contributed and prepared by

Dr Ian Bickle, Department of Radiology,RIPAS Hospital

All images are copyrighted and property of RIPAS Hospital.