Hydronephrosis: Clinical POSTERIOR URETHRAL VALVES, PRESSURE POP-OFFS AND BLADDER FUNCTION

The pop-off mechanisms that sometimes occur with posterior urethral valves have well recognized implications for renal function, such that 1 or both kidneys can be protected from the deleterious effects of elevated bladder pressures. What has not been defined is the significance, if any, of pressure pop-offs to the developing bladder and ultimate bladder function. To answer this question we reviewed the records of 63 boys with posterior urethral valves. Eight boys who were not yet toilet trained had unevaluable bladder outcomes. Of the 55 remaining boys there was 1 or more pressure pop-off in 39 (71%), including massive (grade 5) reflux, massive reflux associated with ipsilateral renal dysplasia, a patent urachus, large diverticula and urinomas. Bladder outcomes were judged as favorable or unfavorable on the basis of urodynamic parameters and/or patient clinical status. A statistically significant positive correlation was found between the presence of a pop-off and a favorable outcome. Favorable characteristics were found in 34 of 39 bladders (87%) with pressure pop-offs. In contrast, only 9 of 16 bladders (55%) without pressure vents had favorable outcomes. In addition, 5 of the remaining 7 boys without pressure vents have required augmentation cystoplasty. A direct correlation between absolute number of pop-offs and favorable bladder outcome was also noted, further emphasizing this relationship. The presence of a pressure pop-off is a favorable prognostic sign for ultimate bladder function in boys with posterior urethral valves. Posterior urethral valves result in variable degrees of renal impairment and bladder dysfunction. The anomaly severely affects some boys but is virtually innocuous in others for reasons that remain unclear. The clinical consequences of valves are undoubtedly dictated by the degree of urethral obstruction and the response of the developing bladder. Otherwise, little is known about why a variable spectrum of manifestations occurs. Some cases of posterior urethral valves are associated with pressure "pop-offs" or vents of the urinary tract. In theory, they could serve to buffer the affected system from the deleterious effects of the elevated intravesical pressures that occur with outlet obstruction. Examples include large bladder diverticula, high grade vesicoureteral reflux, urinomas and a patent urachus. In 1982 Hoover and Duckett described a beneficial relationship between the presence of pressure pop-offs and ultimate renal function in patients with posterior urethral valves.' Infants with unilateral reflux that persisted after valve resection often had ipsilateral renal dysplasia (the syndrome of vesicoureteral reflux and unilateral renal dysplasia). Notably, contralateral renal function and anatomy were usually spared. However, to our knowledge, no study to date has examined the implications of pressure pop-offs for the developing bladder and its ultimate dynamic appearance. Do pop-offs salvage the bladder during a crucial stage in embryogenesis, ultimately allowing preservation of function, or does the presence of a pop-off imply a serious insult early in development that portends poor bladder dynamics later in life? To answer these questions we reviewed * Requests for reprints: Pediatric Urology, Room 1743, Riley Hospital for Children, 702 Barnhill Dr., Indianapolis, Indiana 46202.