Focal Xanthogranulomatous Pyelonephritis on FDG PET/CT.

Xanthogranulomatous pyelonephritis is a rare disease that was often accompanied with urinary obstruction. The focal form of xanthogranulomatous pyelonephritis is frequently misdiagnosed as malignancy. Here we present FDG PET/CT findings of a case focal xanthogranulomatous pyelonephritis in a 66-year-old woman with polycystic liver and kidney disease. The image showed a polycystic mass in the inferior pole of right kidney with high FDG uptake in the cystic wall, which was suggestive of a cystic renal carcinoma. Right radical nephrectomy was subsequently performed. The postsurgical pathology revealed xanthogranulomatous pyelonephritis.