Current epidemiology and antenatal presentation of posterior urethral valves: Outcome of BAPS CASS National Audit.

AIM: Posterior urethral valves (PUVs) are the most common cause of congenital bladder outlet obstruction (BOO) in boys and end-stage renal failure (ESRF) in childhood. In the 1980s, 1 in 4000 boys had PUV. Presentation was 1/3 antenatal/neonatally, 1/3 postnatal, 1/3 late (>1 year). This study aimed to describe the current proportions in a contemporary cohort.

METHODS: A national audit (BAPS CASS) of referrals in the UK and Ireland of boys diagnosed with suspected or confirmed PUV in a year was conducted. National registration data provided the male birth-rate. Data were presented as number (%), analysed by Mann-Whitney U-test and Chi-square test, with P < 0.05 taken as significant. The study was approved by a national ethics committee (NRES Committee South Central Oxford A (12/SC/0416)).

RESULTS: Data were collected from 1st October 2014 to 30th September 2015 from 25/26 centres on 121 cases of suspected bladder outlet obstruction (BOO), of which 113 (93%) were because of PUV. The male birth rate during the period was 432,806/year. The calculated incidence of BOO was 1/3580 and for PUV was 1/3800 per-annum. The proportion of PUV presenting according to age was: antenatally (n = 40, 35%), infancy (n = 47, 42%), and late (n = 26, 23%). Plasma creatinine was higher in antenatally-diagnosed BOO vs. postnatal, 54 (39.5-109.5) μmol/l vs. 34(21-47) μmol/l, P = 0.0005. Hydronephrosis and ureteric dilatation were significantly greater in antenatally diagnosed BOO vs. postnatal vs. late. Renal dysplasia (cortical thinning, poor corticomedullary differentiation, or renal cysts) was significantly more likely in antenatally diagnosed BOO.

CONCLUSION: Neither the incidence (~1/4000) nor the proportion antenatally diagnosed (~1/3) of boys with PUV appears to have changed in the past 30 years. Those boys who were antenatally diagnosed have significantly higher postnatal plasma creatinine, more hydroureteronephrosis, and renal dysplasia than those diagnosed in infancy or later. It may be hypothesized that this is the reason they are detected antenatally.

LEVEL OF EVIDENCE: Prognosis study - Level I - prospective national cohort study.