Xanthogranulomatous pyelonephritis presenting as a cystic mass: a rare case report.

Xanthogranulomatous pyelonephritis may, rarely, occur as a renal cystic mass. We report a case report of a 50-year-old with a history of medically treated renal lithiasis, who consults for left low back pain. Imaging findings concluded to a Bosniak type-3 hemorrhagic cystic mass of the left kidney. The diagnosis of xanthogranumolatous pyelonephritis on its focal form was made histologically. The diagnosis of xanthogranulomatous pyelonephritis is often difficult even with surgical findings and frequently a histological surprise. This points out the importance of identifying it in pre-operative staging; the diagnosis may be suggested by the association of chronic pyelonephritis, renal stones and hypovascular renal tumor syndrome without specificity at sonography and CT.