Objective To explore the prior beliefs regarding the effectiveness of percutaneous vesico-amniotic shunting in congential lower urinary tract obstruction among different clinical specialist groups involved in caring for this condition.

Study design Questionnaire survey of experts in the field based on principles of Bayesian elicitation of prior beliefs. The sample was 59 consultants in three specialties. Of these 37 (63%) were subspecialty trained fetal medicine practioners, 16 (27%) were paediatric nephrologists and 6 (10%) were paediatric urologists.

The questionnaire elicited experts' opinions as to: control arm perinatal mortality, effect of vesico-amniotic shunting on perinatal mortality, current clinical practice and the level of evidence required to change current practice.

Results The response rates were 28% for Fetal medicine specialists, 29% for paediatric nephrolgists and 10% for paediatric urologists. The median belief for Fetal medicine specialists was a 10% (IQR 0–20%) reduction in perinatal mortality with shunting and a mean control arm perinatal mortality of 61%. For Paedaitric nephrologists the results were 5% (IQR 10–15%) and 18% and for Paediatric urologists 10% (IQR 0–15%) and 17%. Fetal Medicine Specialists had the most optimistic beliefs regarding effect of shunting on perinatal mortaility. Thirty eight experts (68%) indicated that vescio-amniotic shunting would most likely reduce morbidity associated with renal dysfunction.

Conclusion The prior beliefs show a divergence of opinion among specialists. This establishes clinical equipoise, which should be resolved with a randomised trial.