Severe obstructive emphysematous pyelonephritis caused by Citrobacter koseri requiring delayed nephrectomy: A case report.

Emphysematous pyelonephritis (EPN) is a life-threatening necrotizing urinary tract infection requiring prompt antimicrobial therapy and source control. An 80-year-old man with diabetes mellitus presented to our emergency department with septic shock. Computed tomography (CT) showed extensive gas formation and abscess cavities extending beyond the right renal parenchyma (Huang-Tseng class 3B) with an obstructing distal ureteral stone. Broad-spectrum antimicrobial therapy and CT-guided percutaneous catheter drainage were initiated. Citrobacter koseri was isolated from drainage fluid, blood, and urine. On hospital day 7, the drainage fluid became urine-like, suggesting urinary leakage; a right single-J ureteral stent was placed for decompression. Because persistent obstruction and extensive renal parenchymal destruction remained despite antimicrobial therapy, percutaneous drainage, and urinary decompression, right nephrectomy was performed on hospital day 15 after hemodynamic stabilization. This case illustrates how repeated clinical and radiological reassessment can guide escalation to delayed nephrectomy in severe obstructive EPN.