Three‐dimensional power Doppler in the diagnosis and surgical management of thoraco‐omphalopagus conjoined twins

Abstract

We report the case of a 28-year-old primigravida in whom we diagnosed thoraco-omphalopagus conjoined twins at 23 weeks' gestation. Further examination revealed a shared liver and separate gall bladders. The twins shared a single umbilical cord. This raised the possibility of sharing of the major intrahepatic vasculature, which could preclude surgical separation. Three-dimensional (3D) power Doppler examination of the hepatic and funic vasculatures was performed using a Voluson ultrasound machine (GE Healthcare Technologies, Milwaukee, WI, USA), equipped with a 3.5-MHz automatic-sweeping transabdominal E8 transducer (Figure 1). This revealed a single three-vessel umbilical cord. The umbilical vein bifurcated into each fetus's hepatic vein, as shown in Figure 2. No major vascular anastomoses were found between the livers of each twin. After extensive counseling, the couple opted for continuation of pregnancy, followed by Cesarean section at 36 weeks' gestation. Postnatal magnetic resonance imaging (MRI) revealed no major shared intrahepatic vasculature. After a tissue expansion procedure, surgical separation was performed successfully at 8 months of age without immediate serious damage to either twin. No major intrahepatic vascular anastomoses were found intraoperatively. Three-dimensional power Doppler image (color mode i.e. with soft tissue subtraction) showing major intra-abdominal and intrahepatic vessels. CHA, common hepatic artery; HA, hepatic artery; HV, hepatic vein; IVC, inferior vena cava; PV, portal vein. Three-dimensional power Doppler image (glass body mode) showing a single umbilical cord with an absence of intrahepatic shared vasculature. HV, hepatic vein; UV, umbilical vein. The chance of successful postnatal separation of conjoined twins depends on the complexity of vital organ fusion1. For omphalopagus twins, the degree of fusion of the hepatobiliary and gastrointestinal systems is not easy to determine prenatally and can pose a significant surgical challenge2. In one reported case, the major vascular connections within a shared liver were demonstrated postnatally and this significantly affected the surgical procedures that were performed3. Portal veins can be demonstrated by Doppler examination in 94% of fetuses that are more advanced than 20 weeks' gestation4, which implies that sonographic examination should be able to identify any major vascular connections from this gestational age onwards. The advent of power Doppler ultrasonography, in combination with 3D imaging, has allowed visualization of the intrahepatic vasculature in multiplanar and simulated 3D images. 3D imaging of vascular structures can also be accomplished using high-definition color Doppler. This report suggests a further application of these novel imaging technologies in the management of conjoined twins and other complex vascular malformations. 3D imaging technology allowed the examiner to visualize the target organs from limited insonation angles, which are commonly encountered during the examination of multifetal pregnancies. MRI offers an alternative method of investigating shared vasculature in the liver5. It provides sharp soft tissue delineation, but, owing to the complicated protocol and cost, MRI should be reserved for patients for whom it is not possible to obtain optimal images on ultrasound examination. 3D sonographic vascular imaging has clear advantages in terms of its noninvasiveness and convenience, and is also more suitable for use in patients who suffer from claustrophobia. T. Wataganara*, A. Sutanthaviboon*, S. Ngerncham , C. Vantanasiri*, * Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Faculty of Medicine Siriraj Hospital, Mahidol University, 2 Prannok Road, Bangkoknoi, Bangkok, Thailand 10700, Division of Neonatology, Department of Pediatrics, Faculty of Medicine Siriraj Hospital, Mahidol University, 2 Prannok Road, Bangkoknoi, Bangkok, Thailand 10700