Left renal mass ABDOMEN:LIVER, BILIARY TRACT: No significant abnormality noted.SPLEEN: Subcentimeter cyst. Otherwise, no abnormality noted.PANCREAS: No significant abnormality noted.ADRENAL GLANDS: No significant abnormality noted.KIDNEYS, URETERS: Multiple non-enhancing bilateral renal cysts. RETROPERITONEUM, LYMPH NODES: There is an approximately 8.7 x 7.3 x 8.5 cm mass inferior and medial to the left kidney, displacing the left kidney superiorly. The mass is predominantly composed of fat. There is internal vasculature and enhancement, with an artery extending from the left renal artery into this mass. The left-sided hydronephrosis and probable calyceal diverticula are similar to the prior CT. The renal calculi seen on the prior CT are not evident on the current MR, likely secondary to technique.BOWEL, MESENTERY: No significant abnormality noted.BONES, SOFT TISSUES: Areas of linear enhancement in the lower anterior abdominal wall likely reflect prior surgery. No significant abnormality noted.
Large fat-containing enhancing mass inferomedial to the left kidney, most likely representing a pedunculated angiomyolipoma. A retroperitoneal liposarcoma is less likely.  