Anaerobic bacterial infection and xanthogranulomatous pyelonephritis: a case report.

A young man presented with a history of uncorrected ureteropelvic junction obstruction 18 months in duration and clinical acute pyelonephritis. Retrograde pyelography showed unilateral pyonephrosis and cultures of purulent drainage proximal to the ureteropelvic junction revealed predominantly anaerobic bacteria and no aerobic gram-negative bacilli. Subsequent nephrectomy established a diagnosis of xanthogranulomatous pyelonephritis. Nephrectomy in combination with intensive antimicrobial therapy resulted in recovery. The contribution of anaerobic bacteria in the pathogenesis of xanthogranulomatous pyelonephritis is unknown. Anaerobic culture of urine and excised tissue in these patients may be indicated.