Acute renal failure due to pyelonephritis.

Acute renal failure developed in a 3-year-old boy with acute pyelonephritis. Renal biopsy showed acute interstitial infiltration of neutrophils and macrophages. There were also glomerulitis and capillary tuft thrombosis. He required peritoneal dialysis, but subsequently recovered renal function. Prompt antimicrobial therapy is crucial to insure a favorable outcome. Pyelonephritis is an unusual cause of acute renal failure in infants and children.