Imaging in the preoperative assessment of conjoined twins

Conjoined twins are rare and present a unique challenge to pediatric surgeo ns and radiologists. Planning of surgical separation is aided by accurate p reoperative imaging. Such twins are classified according to the most promin ent site of connection: the thorax (thoracopagus), abdomen (omphalopagus), sacrum (pygopagus), pelvis (ischiopagus), skull (craniopagus), face (cephal opagus), or back (rachipagus). The area of fusion largely determines the im aging modalities used. Thoracic conjunction is most common and requires car diac assessment. Magnetic resonance imaging and computed tomography provide excellent anatomic and bone detail, demonstrating organ position, shared v iscera, and limited vascular anatomy. Contrast material radiography allows evaluation of the gastrointestinal and urogenital tracts, and a shared live r requires assessment of anatomy, vascularization, and biliary drainage. An giography helps define specific vascular supply, which is useful in determi ning the distribution of shared structures between the twins at surgery. Ea ch set of conjoined twins is unique. An imaging strategy to accurately defi ne anatomic fusion, vascular anomalies, and other associated abnormalities is important for surgical planning and prognostic information.