A Path Less Traveled: Xanthogranulomatous Pyelonephritis Presenting with Thoracic Empyema and Complicated By Rare Pyeloduodenal Fistula.

Xanthogranulomatous pyelonephritis (XGP) is a rare and diffusely destructive variant of pyelonephritis. Diagnosis is made using the characteristic radiological findings of renal enlargement with pelvicalyceal dilatation (the 'bear paw' sign) with histological analysis demonstrating replacement of renal parenchyma with foamy lipid-laden histiocytes. Treatment of XGP invariably requires nephrectomy. Two particularly rare complications of XGP are thoracic empyema and pyeloduodenal fistula; this case, to our knowledge, is the first such instance of XGP complicated by both. The patient underwent chest drain placement for treatment of empyema, and, following the identification of the pyeloduodenal fistula on antegrade pyelography, underwent surgical treatment with partial right-sided colectomy, radical nephrectomy, and primary duodenal fistula closure. XGP was subsequently identified on pathological analysis of the removed kidney.