Robotic Heminephrectomy for Xanthogranulomatous Pyelonephritis in a Pediatric Patient.

Xanthogranulomatous pyelonephritis (XGP) is a rare, chronic, destructive inflammatory condition of the kidney characterized by progressive renal parenchymal loss and replacement with lipid-laden macrophages, granulomatous inflammation, and fibrosis. In adults, XGP most commonly affects middle-aged women and is typically associated with urinary tract obstruction, nephrolithiasis, and recurrent infection. In contrast, pediatric XGP is exceptionally uncommon, with reported cases largely limited to isolated case reports and small case series. Pediatric presentations are frequently atypical, often lacking classic risk factors and instead manifesting with nonspecific symptoms or as an incidental renal mass. This creates a significant diagnostic dilemma, as focal XGP can radiographically mimic renal malignancy, abscess, or congenital renal pathology, with definitive diagnosis often established only after surgical resection. We report the case of a 14-year-old male without a history of nephrolithiasis or recurrent urinary tract infections who was incidentally found to have a large left renal upper pole mass on computed tomography (CT) imaging obtained during evaluation for an unrelated condition. Imaging revealed a complex solid and cystic lesion measuring 11.5 × 7.9 × 10 cm with multiloculation, septations, perinephric inflammatory changes, and urothelial thickening, raising concern for malignancy versus complicated infection. Interventional radiology-guided nephrostomy tube placement drained purulent fluid, and cultures grew