Extrauterine twin-twin transfusion syndrome after birth in conjoined twins.

Cross-circulation of conjoined twins in utero has been demonstrated and the extent of its severity has varied. Significant 'extrauterine' twin-twin transfusion syndrome after birth, however, caused by an unbalanced shunting within the circulation has not been reported. In a case of omphalopagus conjoined twins complicated by hypovolemia in one twin and hypervolemia in the other, we demonstrated by color Doppler imaging an aberrant vessel from the hepatic artery of one twin to the hepatic vein of the other. Unbalanced shunting through this aberrant vessel was suspected and urgent separation of the conjoined twins was undertaken. Circulatory changes after birth leading to 'extrauterine twin-twin transfusion syndrome' are discussed. A possible explanation of the pathophysiology of intrauterine twin-twin transfusion syndrome is also given.