P05.14: A novel case of monochorionic diamniotic conjoined twins with genitourinary and gastrointestinal union

In this report we describe a case of conjoined twinning initially diagnosed as monochorionic diamniotic twins. Early ultrasounds documented the presence of a thin intertwin membrane. On later ultrasounds one twin appeared to have restricted mobility and the intertwin membrane was no longer visible suggesting the diagnosis of early twin to twin transfusion syndrome. The twins were found to be conjoined and a 2–3 cm band of tissue connecting the twins was delineated in the lower abdomen consistent with the omphalophagus type of conjoined twinning. Amniotic fluid appeared normal around the mobile twin. A bladder could not be delineated for either twin nor could genitalia be identified. These findings, coupled with the abdominal connection of the twins suggested the diagnosis of bladder extrophy for both twins. A fetal MRI was consistent with these conclusions and also suggested other subtle limb abnormalities in the fixed twin. The mother underwent TOP at 21weeks and delivered vaginally. The autopsy revealed several interesting findings which are unusual for this type of conjoined twinning. Autopsy of the fetuses confirmed the diagnosis of omphalophagus conjoined twins with both internal and external union at the level of the umbilicus. The distal small bowel and entire large bowel was shared, there was anal atresia and the rectum opened into a shared bladder with extrophy. There was union of their urogenital systems. The region of fusion included a shared bladder which connected with an outlet for the urinary and reproductive systems. Pathological assessment of the placenta and membranes suggested the twins were separated by an amniotic membrane created by rupture of the amnion later in gestation. This case demonstrates an interesting case of conjoined twinning where early ultrasound clearly suggest diamniotic twins. In addition to union of the gastrointestinal systems there was union of the genitourinary systems which is unusual in omphalophagus conjoined twins.