Answer

CT Renal Abscess

There is a low density cystic structure in the anterior aspect of the right kidney At the level where it bulges beyond the confines of the kidney there are soft tissue changes in the perinephric fat and extending to the properitoneal fat.  A small enhancing medial rim may be part of the abscess or part of the kidney. These findings are not absolutely pathognomonic but in the appropriate clinical setting the diagnosis of abscess would be most likely.  Next step would be percutaneous drainage under imaging guidance

Ashley Davidoff MD TheCommonVein.net