Posterior urethral valves: prognostic factors

To determine which variables besides bladder dysfunction can help to predict the outcome of renal function in boys with posterior urethral valves (PUV).

All 40 patients with PUV in this retrospective study were diagnosed and began treatment in our hospital within the first 3 months of life, and have had >or= 5 years of follow-up. At the time of diagnosis, 33 were in renal insufficiency (RI) and seven had normal renal function (RF). At the time of the study 16 were in chronic renal failure (CRF) and 24 had normal RF. We compared their RF (initial and during follow-up), vesico-ureteric reflux (VUR), urinary tract infection (UTI), proteinuria, hypertension, renal echogenicity, final patient age and initial management.

The mean serum creatinine values before and after initial treatment were worse in boys who developed CRF than in those who did not (P = 0.08); the mean glomerular filtrate rate (GFR) at 1 year old was 52 mL/min/1.73 m2 in the former and 102 in the latter (P < 0.001). Proteinuria was present during the follow-up in 79% of patients in CRF and in only 17% of those with normal RF. All patients who developed CRF had echogenic renal changes while only 53% of the others had (P < 0.01). Other variables showed no statistically significant differences (VUR, UTI, hypertension and final patient age). Of 33 patients in RI at diagnosis, nine were treated by valve ablation and 24 by temporary pyelo-ureterostomy. The initial mean serum creatinine value was worse in the latter than in the former (20.8 vs 13.0 mg/L). However, at 1 year old the mean GFR was better in the latter than in the former (P < 0.05). These GFR differences persisted during the first years of life but had disappeared by the fifth.

The most significant prognostic factor for the future development of CRF is the GFR at 1 year old. The onset of proteinuria during the follow-up is associated with a worse prognosis. Echogenic renal changes may help to identify those dysplastic kidneys that will develop RI. Neonatal boys in RI who underwent pyelo-ureterostomy had better RF during the first years of life than those who underwent valve ablation.