A Morphological Study on Conjoined Twins in Korea

Abstract

General morphological patterns of major organ systems in various types of conjoined twins are described. Sixteen pairs of conjoined twins used in this study were five thoracopagi, four dicephalic twins, four cephalothoracopagi, a craniopagus, a dicephalus dipygus and a heteropagus. The fusion of skeletal systems was closely related to the external morphology. The central nervous system was always duplicated. Nose and oropharynx patterns were determined by the number of faces, but the lower respiratory organs were always duplicated. The digestive tract was related to the skeletal union but the level of union and duplication varied. The liver was frequently fused in the cases of truncal union except in cephalothoracopagi. Genitourinary system patterns were related to the number of legs. Cardiovascular systems showed five distinct types of vascular union. The umbilical vessels were related to the number of trunks, but variations existed. In the fusion of symmetrical conjoined twins, there appeared to be certain rules that can be summarized as follows. The twin pairs tended to face each other. The fused portion was in the frontal plane, whereas the rest of the bodies were in lateral planes. Conjoining of the bodies in side-by-side pattern was associated with the same inner sides. In Korea, we seem to have a higher relative incidence of cephalothoracopagus and dicephalus, whereas in other countries thoracopagus is the predominant type.