Thoracopagus conjoined twins are, as the name suggests, conjoined twins united at their thorax. Thoracopagus and thoraco-omphalopagus form the most common forms of conjoined twins 3.
Fusion is typically face-to-face, at the upper thorax to the umbilicus with a common sternum, diaphragm, and upper abdominal wall. Very often a common pericardial sac is present as well as a degree of cardiac fusion, which makes surgical intervention difficult, if not impossible.
Liver and biliary tree fusion are also noted in a quarter of cases. Less commonly, a fusion of the small intestine may also be encountered.
The pelvises, large intestines, and urinary tracts are usually separate.
Antenatal fetal echocardiography is imperative in these cases, with further evaluation performed during the postnatal period. Cardiac angiography and cardiac MRI may also be required to fully evaluate the anatomy.