Urinary tract obstruction and infection in the neonate.

Congenital urinary tract obstruction is a common cause of renal failure accounting for up to 20% of end-stage renal disease cases. Intrauterine obstruction often results in parenchymal loss and renal dysfunction. The pathophysiology of obstructive nephropathy and its further depression of renal function is related to severe renal vasoconstriction, which is in large part angiotensin mediated. Signs suggestive of urinary obstruction in the newborn may include an abdominal mass, hypertension, oligoanuria/polyuria, urosepsis, and hyperchloremic acidosis. The combination of renal ultrasound, diuretic renal scans, and voiding cystourethrogram are the main diagnostic modalities in infants with hydronephrosis. Nonsurgical management of ureteropelvic junction obstruction has become more popular, particularly in mild to moderate cases. Early fulguration or bypassing the obstruction of urethral valves is essential and a decrease in serum creatinine to below 1 mg/dL within 1 month of relief of obstruction is a favorable prognostic sign. Obstruction complicated by infection is dangerous and requires prompt intervention. Any newborn with a urinary tract infection, regardless of sex, should be presumed to have urinary obstruction or reflux until proven otherwise.