Norwich-Eaton lectureship. Pathogenesis of nonobstructive urinary tract infections in children.

Most urinary tract infections occur without either obstruction or vesicoureteral reflux. Children become colonized by their mother's bacterial flora, that within the nursery or by siblings. Bacterial adherence may lead to colonization of the perineum in girls and of the prepuce in boys (if uncircumcised). Nephropathogenic bacteria ascend the urinary tract because of the P-fimbriae of Escherichia coli which adhere to a specific urothelial cell glycolipid. The endotoxin effect on ureteral peristalsis leads to intrarenal reflux, adherence in the kidney and acute pyelonephritis. Complement activation then causes granulocytic aggregation in capillaries with renal ischemia and activates granulocytes to produce the respiratory burst of phagocytosis, which releases superoxide into both phagosomes and the tubular lumen. Bacteria are thus killed as are renal tubules, leading to nephron loss. Untreated, the ischemia and respiratory burst lead to a loss of renal function and scar formation ending as chronic pyelonephritis (or reflux nephropathy).