Early prenatal diagnosis of concordant posterior urethral valves in male monochorionic twins

Rare Associations with Posterior Urethral Valves

Posterior urethral valves are a common cause of congenital bladder outlet obstruction. Known associations include cardiac malformations and gastrointestinal abnormalities. In this case series, we report on two cases of PUV associated with anorectal malformations along with a case of PUV in monochorionic diamniotic twins. We explore the difficulty in achieving a diagnosis and the final management. The association of posterior urethral valves in a patient with anorectal malformation should be suspected in case of associated oligohydramnios or oliguria postnatally. There should be a high index of suspicion in twin pregnancy even if only one of the twins is suspected of bladder outlet obstruction.

A classic twin study of lower urinary tract obstruction: Report of 3 cases and literature review

OBJECTIVE

The aim of the present study was to investigate genetic effects in the formation of congenital lower urinary tract obstruction (LUTO) comprising posterior urethral valves (PUV), urethral atresia, and urethras with variable degrees of stenosis.

METHODS

A classic twin study was performed by assessing LUTO twin pairs from the literature. Furthermore, data regarding 3 previously unreported twin pairs with PUV from University of Bonn, Essen and Wrocławs own in-house databases were added. Both pair- and probandwise concordance rates were calculated and compared for monozygotic (MZ) and dizygotic (DZ) twin pairs.

RESULTS

The pairwise concordance rates for all LUTO were 53% (95% confidence interval [CI] 32%-73%) and 17% (95% CI 3%-56%) for MZ and DZ twin pairs, respectively (P = .180). The probandwise concordance rates were 69% (95% CI 51%-83%) and 29% (CI 95% 8%-64%) for MZ and DZ twin pairs respectively (P = .084). The MZ/DZ ratios of the pair- and probandwise concordance rates were 3.1 and 2.4, respectively.

CONCLUSION

The present study did not show significant differences in comparisons of concordance rates of MZ and DZ twin pairs, probably due to the small number of twin pairs reported. However, the more than 2-fold higher pair- and probandwise concordance rates for MZ versus DZ twin pairs are very suggestive of a contribution of genetic factors to the development of LUTO.