Thoraco-abdominal anomalies in a dicephalic parapagus twin

Conjoined twins represent a rare but fascinating congenital condition, the aetiology of which remains obscure. 'Parapagus' is a fairly new term, in which the twins lie side to side, with ventrolateral fusion but there is some confusion in the literature. Parapagus twins arise from streaks that lie adjacent to one another, potentially allowing cross-signaling to occur, with the development of laterality defects. In this article, we demonstrate the various anomalies of the thoracic and the abdominal cavity, with an embryological reason behind their development. An accurate antenatal assessment allows the parents to be counseled in depth as to the likely outcome of the pregnancy and the chances of postnatal separation and survival.