Prenatal diagnosis of Abernethy malformation by three-dimensional ultrasonography.

Abstract

Abernethy malformation is an abnormal portosystemic shunt that was first described in 1793 as a postmortem finding1. Prognosis is determined primarily by the extent of the portal system development2, which classifies the malformation into one of two types: Type 1, or classical Abernethy malformation, in which portal blood is diverted completely into the inferior vena cava (IVC) with absence of the portal vein, and is associated with hepatic failure and hepatic tumors; and Type 2 in which the portal vein is intact, and thus conveys a better prognosis3. A 25-year-old primigravida was referred to our center at 23 weeks' gestation due to detection of an abnormal blood vessel of large diameter in the fetal abdomen. On two-dimensional (2D) ultrasound examination (GE Voluson E8 Expert, GE Medical Systems, Zipf, Austria) the vessel had a monophasic Doppler waveform and direction of flow was towards the pelvis. The ductus venosus was present and the IVC was dilated. Analysis of three-dimensional (3D) color Doppler volumes with glass-body mode and four-dimensional (4D) spatiotemporal imaging correlation (STIC) showed that the aberrant vessel originated from the intrahepatic segment of the umbilical vein (UV) (Figure 1). The vessel passed above the left common iliac vein and, following a U-turn course in the fetal pelvis, anastomosed with the IVC at the level of its bifurcation (Figure 2). With 3D power Doppler rendered images we were able to conclude that the vessel originated from the intrahepatic segment of the UV, coursing sharply to the left in the fetal abdomen, anterior to the dilated IVC. Initially, on 2D ultrasound, the aberrant vessel was assumed incorrectly to originate from the IVC. This important differentiation established the diagnosis of a portosystemic shunt, and 3D power Doppler and 4D STIC rendered images enabled visual reconstruction of the complex course of the vessel in the fetal pelvis. By studying stored 3D Power Doppler volumes we were able to examine the fetal portal vessels and conclude that the right branch of the portal vein, which should be visualized easily in the normal fetus4, was clearly absent. In addition, we were unable to visualize the main portal vein (MPV) resulting in a possible diagnosis of Abernethy Type 1. Postnatal magnetic angiography 5 days after delivery demonstrated a thin MPV, formed by the splenic and superior mesenteric vein (Figure 3) and the malformation was reclassified consequently as Abernethy Type 2. The discrepancy between prenatal and postnatal findings regarding presence of the MPV could be explained by either the increased sensitivity of postnatal magnetic angiography compared to prenatal ultrasonography or the relatively reduced flow in these vessels during the fetal state of circulation5. In conclusion, use of 3D reconstructed Doppler images enables detailed examination of the anatomy of the fetal venous system and its malformations. We have demonstrated application of this imaging technology in prenatal diagnosis of Abernethy malformation. We would like to thank Dr C. Pachoumi and Mr J. Dimitrakopoulos for their contribution and technical assistance in the rendering of images.