Morphological variations on vital systems in a conjoined twin.

Conjoined twins (CTs), popularly referred to as Siamese twins, are a rare anomaly due to monochorionic and monoamniotic twin pregnancies. Dicephalus dibrachius dipus, a type of parapagus conjoined twin which is characterized by possessing two arms, two legs, a single trunk and two heads, epidemiologically, is an even rarer occurrence of CTs. In this article, a rare, well-preserved anatomical specimen of a dicephalus dibrachius dipus conjoined twin is presented. This study was conducted in a specimen which is part of the collection of the Embryology Museum of the institution by donation and approved by the Research Ethics Committee (REC). The female conjoined twins were born at full-term by cesarean section in the 1970s and died hours after birth. A thorough anatomical description was made through observational analysis, computed tomography and 3D reconstructed images. Major abnormalities were observed in the cardiovascular, respiratory and digestive systems. The internal anatomy exhibited a heart with three atria, two ventricles, two aortic arches, two pulmonary arteries, one innominate venous trunk and a respiratory system with two tracheas and four lungs. No other report was similar to our three atria heart description. This article provides a thorough anatomical description of all systems, which is valuable information for further studies on CTs.