Mri of renal angiomyolipomas

The MR appearance of 13 renal angiomyolipomas in 11 patients were reviewed. The fatty tissue in angiomyolipomas which demonstrated hyperintensity on Tl-weighted imaging was considered to be a key point for diagnosis with MRI. Renal angiomyolipomas were classified into three types according to the proportion of fatty tissue in tumours. Fatty tissue comprises more than 80% of the volume of an angiomyolipoma in type I, 20–80% in type II and less than 20% in type III tumours. It was easy to diagnose types I and II renal angiomyolipomas with MRI, but it was quite difficult to differentiate type III renal angiomyolipomas from other solitary occupying lesions such as renal cell carcinoma. Other MR characteristics of renal angiomyolipomas are summarized and are thought to have diagnostic uses.