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 Proteus species, an organism commonly associated with XGP. Despite intravenous antibiotic therapy and drainage, repeat imaging demonstrated persistent lesion size and inflammatory burden. Given ongoing concern for a non-resolving renal mass, the patient underwent robotic-assisted left upper pole heminephrectomy. Intraoperatively, the upper pole was grossly abnormal with no viable renal parenchyma and a large abscess cavity. Final histopathologic evaluation confirmed focal XGP. Although rare in children, XGP should remain on the differential diagnosis for complex renal masses, particularly when imaging demonstrates inflammatory or abscess-like features. This case highlights the diagnostic challenge of pediatric focal XGP and demonstrates the feasibility of a robotic-assisted nephron-sparing heminephrectomy approach in carefully selected patients. Early recognition of this entity may help guide timely surgical intervention while avoiding overtreatment for presumed malignancy and preserving functional renal tissue whenever possible.
Akhdar et al. (2026) studied this question.