Xanthogranulomatous Pyelonephritis with Spontaneous Nephrocutaneous Fistula

Xanthogranulomatous pyelonephritis is a severe, rare, form of chronic pyelonephritis characterized by the destruction of the renal parenchyma and replacement by granulomatous tissue.This disease has been called as the “great imitator” because clinical and radiological findings often mimics other inflammatory or neoplastic renal disorders leading to diagnostic challenge before histopathologic analysis. Herein, we report a case of a 72-years-old woman who presented with a 4-year history of left flank pain with intermittent lumbar purulent discharge. The CT scan findings advocated a pyonephrosis. After a left nephrectomy, the per-operative and macroscopic appearance of the mass was in favor of a renal replacement lipomatosis. Microscopic examination finally revealed the diagnosis of Xanthogranulomatous pyelonephritis. Clinicians, radiologists and pathologists should be aware of this rare “great imitator” entity.