Biliary atresia: From Australia to the zebrafish.

This review is based upon an invited lecture for the 52nd Annual Meeting of the British Association of Paediatric Surgeons, July 2015. The aetiology of biliary atresia (BA) is at best obscure, but it is probable that a number of causes or pathophysiological mechanisms may be involved leading to the final common phenotype we recognise clinically. By way of illustration, similar conditions to human BA are described, including biliary agenesis, which is the normal state and peculiar final pattern of bile duct development in the jawless fish, the lamprey. Furthermore, there have been remarkable outbreaks in the Australian outback of BA in newborn lambs whose mothers were exposed to and grazed upon a particular plant species (Dysphania glomulifera) during gestation. More recent work using a zebrafish model has isolated a toxic isoflavonoid, now named Biliatresone, thought to be responsible for these outbreaks. Normal development of the bile ducts is reviewed and parallels drawn with two clinical variants thought to definitively have their origins in intrauterine life: Biliary Atresia Splenic Malformation syndrome (BASM) and Cystic Biliary Atresia (CBA). For both variants there is sufficient clinical evidence, including associated anomalies and antenatal detection, respectively, to warrant their aetiological attribution as developmental BA. CMV IgM +ve associated BA is a further variant that appears separate with distinct clinical, histological, and immunohistochemical features. In these it seems possible that this involves perinatal obliteration of a normally formed duct system. Although still circumstantial, this evidence appears convincing enough to perhaps warrant a different treatment strategy. This then still leaves the most common (more than 60% in Western series) variant, now termed Isolated BA, whereby origins can only be alluded to.