The contribution of modern imaging to planning separation strategies in conjoined twins

An accurate knowledge of the often complex and unexpected anatomy of conjoined twins is required in order to devise appropriate surgical strategies for separation. The recent progress of imaging techniques prompts an assessment of their contribution to planning separation strategies.

From 1990, we treated 8 consecutive sets of conjoined twins: 1 acardiac-acephalus, 1 epigastric heteropagus, 2 omphalopagus, 2 omphalothoracopagus, 1 ischiopagus tetrapus and 1 parapagus tripus. The first two sets were separated straightforwardly after birth and were excluded. Ultrasonographic and plain and contrast X-ray studies were used in all the remaining sets, angiography in 5, CT in 4, and MRI in 4. Helical CT and magnetic resonance angiography (MRA) were used in 3 sets.

Two sets of omphalopagus twins and one of omphalothoracopagus twins were separated after birth due to brain damage of one twin, cloacal exstrophy and large arterial shunting, respectively. They were assessed using barium studies (3 sets), IVP (3), angiography (2), CT (2) and MRI (1). Three of six babies survived after separation. In the second set of omphalothoracopagus ecocardiography and MRA revealed that the extent of cardiovascular sharing precluded separation. In the remaining two sets of twins respectively ischiopagus and parapagus, the extent of organ sharing was depicted using three-dimensional helical CT and MRI; the four babies are alive after separation.

Conventional imaging contributes only modestly to separation planning. In contrast, advanced imaging techniques are amazingly efficient in depicting complex fusions that have to be accurately recognised when planning realistic separation strategies.