Focal Xanthogranulomatous Pyelonephritis (a Pseudotumour) associated with Retroperitoneal Fibrosis: Case report

Abstract

Xanthogranulomatous Pyelonephritis (XGP) is a rare form of renal granulomatous inflammatory disease. Two forms of XGP are well described; a diffuse form (85%) and a focal form (15%). Preoperative diagnosis of focal XGP is uncommon as it radiologically and clinically mimicks renal cell carcinoma. Therefore, the focal form is also referred to as the ‘tumefactive form’. The definitive diagnosis of focal XGP is made only after histo-pathologic examination of the resected specimen in which characteristic lipid laden macrophages are seen. We present an interesting case of a 65-year-old male who had left lumbar pain. A preoperative diagnosis of renal cell carcinoma was made on CT. On histologic analysis, a final diagnosis of focal XGP was revealed. Although rare, focal XGP should be considered as the main differential for renal malignancy.