Xanthogranulomatous Pyelonephritis: a rare presentation

Nova Southeastern University, Davie, Florida, USA

Introduction. Xanthogranulomatous Pyelonephritis (XGP) is a rare subtype of chronic pyelonephritis. It results in a large renal mass and is challenging to differentiate from other masses/lesions. Most cases affect diabetic middle-aged females with chronic UTIs or nephrolithiasis. Case Presentation. A 21-year-old female from Venezuela presented to the ED with two days of LUQ pain, two weeks of watery diarrhea, and 20lbs of unintentional weight loss. She denied any urinary symptoms, history of UTIs or nephrolithiasis. Workup revealed anemia, leukocytosis, and sterile urinalysis. On CT, the left kidney was 15.4x12.2x17.2cm, obliterated by loculated cystic spaces, with staghorn calculi. Adjacent stranding and lymphadenopathy raised concern for pyelonephritis and malignancy. Two percutaneous nephrostomy tubes drained over 450ml of pus that grew Proteus. Urology performed robotic left nephrectomy with pre/postoperative antibiotic treatment, and pathology confirmed XGP. Deviation from the Expected. XGP most often affects diabetic middle-aged women with chronic UTIs or nephrolithiasis. Our case emphasizes the variability of this disease. Though preoperative nephrostomy tube drainage is standard, placing multiple tubes is a unique strategy. Discussion. Early studies pinpointed XGP in 0.6% of nephrectomies performed for chronic pyelonephritis. Modern incidence estimates are 4-18%. The pathophysiology is mysterious but involves chronic inflammation from infectious/obstructive processes. Abundant lipid-laden macrophages produce a grossly yellow appearance. XGP is often confused for malignancy, but renal tuberculosis, congenital polycystic kidney disease, and pyonephrosis are also differentials. Conclusion. XGP may be more common than initially thought. Familiarity is essential, as it is easily confused with other renal masses/lesions. Grants. This study was non-funded.