Vesicoureteral reflux in infants

Grade 5 vesicoureteral reflux (VUR) is almost exclusively seen in male infa nts, and in one-third of cases occurring with a generalized small kidney wi th decreased renal function without a previous history of urinary tract inf ection. In females, however, high-grade reflux is rare and kidney damage al most always less severe and of the focal, type, as in older children. Asses sment of the bladder function with urodynamic and free voiding studies also indicates a difference between male and female reflux during infancy. Half of the males with dilating reflux initially have a hypercontractile urodyn amic pattern indicating small functional capacity with high voiding pressur es and often instability during filling. This pattern changes during the fi rst couple of years to high-capacity over-distended bladders, often with in complete emptying. In females, hypercontractility is seldom seen, but bladd er function is characterized by high capacity and there is an increase in r esidual urine from presentation. The pathogenesis of VUR has also been sugg ested to differ between the sexes. Transient anatomical obstruction during fetal life has been proposed as the cause of gross VUR in males. The sponta neous resolution rate of dilating infant VUR seems to be significantly high er than in older children. A resolution of 40% of grades 4 and 5 has been r eported during the first couple of years in prenatally diagnosed cases, sug gesting that antireflux surgery should be postponed until after the infant year.