Multifocal xanthogranulomatous inflammation of the urinary tract mimicking metastatic urothelial carcinoma: A case report

RATIONALE: Xanthogranulomatous inflammation (XGI) is a rare chronic granulomatous disorder characterized by lipid-laden macrophage infiltration and most commonly involving the kidney and gallbladder. Multifocal urinary tract involvement is exceptionally rare and may radiologically mimic metastatic malignancy, particularly on positron emission tomography-computed tomography (PET/CT). PATIENT CONCERNS: A 67-year-old woman with long-standing diabetes mellitus and hypertension presented with left hydronephrosis, recurrent urinary tract infections, and progressive renal dysfunction. PET/CT demonstrated extensive hypermetabolic lesions involving the bladder, ureters, renal pelvis, and retroperitoneal lymph nodes, raising suspicion for metastatic urothelial carcinoma. DIAGNOSES: Multifocal xanthogranulomatous inflammation involving the bladder and ureter, with radiologically suspected upper urinary tract involvement. INTERVENTIONS: The patient underwent transurethral resection of the left ureteral orifice and bladder lesions, bilateral nephrostomy, renal abscess drainage, and antibiotic therapy. OUTCOMES: Repeated histopathological and immunohistochemical examinations consistently excluded malignancy and confirmed xanthogranulomatous inflammation. Following surgical drainage and anti-infective treatment, infection parameters improved substantially, and the patient was discharged in stable condition. LESSONS: PET/CT hypermetabolism does not exclude inflammatory disease. When imaging findings strongly suggest malignancy, repeated histopathological evaluation remains essential for establishing an accurate diagnosis. Multifocal urinary tract XGI should be considered in the differential diagnosis of PET-positive urinary tract lesions, particularly in patients with diabetes and recurrent urinary tract infections.