The imaging spectrum of conjoined twins

Conjoined twins are a rare complication of monochorionic twinning. Although most conjoined twins are stillborn or die in the newborn period, surgical advances are such that many parents will continue a pregnancy in the hopes that live born infants can be separated. Well-described types of conjoined twins account for most cases, with some rarer forms occasionally seen. Each type is associated with specific degrees of organ sharing, structural abnormalities, complications, and challenges with regard to potential separation. Thorough multidisciplinary prenatal assessment of conjoined twins is essential to appropriately counsel parents, to manage the pregnancy, and to create an appropriate delivery plan. This pictorial essay presents the imaging findings of the more common types of conjoined twins. Selected clinical and autopsy images are used to illustrate shared anatomy. The nomenclature for description of conjoined twins is reviewed, the imaging findings of each type are illustrated, and the challenges to separation are discussed.