Heteropagus Twins with Hepatobiliary and Gastrointestinal Connectedness and Complex Cardiac Malformation in Autosite

Introduction: Heteropagus twins are a set of conjoined twins with one being grossly abnormal, the ‘parasite’, and the other being relatively normal, the ‘autosite’. Case Report: A pair of heteropagus twins were initially identified on prenatal ultrasound and subsequently confirmed using prenatal MRI at 25 weeks gestational age. Prenatal imaging identified supernumerary limbs, accessory small bowel loops in the parasitic twin, a hypoplastic left heart in the right hemithorax of the autosite, and a shared liver and bowel between the two. Delivery occurred at 38 + 5 weeks gestation via C-section with an APGAR score of 9/9 for the autosite at both 1 and 5 minutes. MRI confirmed an interconnected autosite-parasite liver that was herniating into the left hemithorax as well as continuous autosite-parasite bowel loops. The patient underwent surgical management including resection of the parasitic twin and repair of the congenital heart defect and is now thriving. Discussion: Heteropagus twins include a spectrum of clinical entities from nonconjoined twins to intact conjoined twins. The predominant theory regarding etiology is an incomplete cleavage of a monozygotic embryo at approximately 2 weeks gestation. Following differentiation, ischemia-induced atrophy leads to the embryonic death of the parasite and hemodynamic changes in the autosite to support parasite tissues. The use of antenatal and postnatal imaging is crucial in establishing the diagnosis, management plan, and longterm prognosis secondary to the congenital cardiac malformations and degree of interconnectedness. Conclusion: This is the first reported case of heteropagus twins with co-existing hepatobiliary and gastrointestinal continuity.