Prenatal diagnosis of two intrahepatic portosystemic shunts associated with absence of ductus venosus.

Abstract

Congenital portosystemic shunts (CPSS) are defined as abnormal communications between the portal venous system and the systemic circulation. Their classification is complicated and variable, usually based on the origin of the shunt (intrahepatic or extrahepatic). CPSS may appear as an isolated anomaly or be associated with other congenital anomalies1, 2. The diagnosis is usually made postnatally1, 2, and the timing of its appearance depends on the clinical presentation (hepatic encephalopathy, hepatopulmonary syndrome, portal hypertension, liver tumors). Incidental diagnosis of CPSS on imaging for unrelated reasons is not uncommon. Based on improvements in understanding of the embryology and anatomy of the fetal precordial venous system, researchers have introduced a systematic protocol allowing for the prenatal ultrasound diagnosis of CPSS3-5. We describe a rare presentation of CPSS associated with agenesis of the ductus venosus, that was diagnosed prenatally. A 30-year-old woman, gravida 3, para 2, was referred to our ultrasound unit at 30 + 0 weeks' gestation for assessment of a hyperechogenic fetal bowel detected a few weeks previously. Nuchal translucency, biochemical screening tests and anatomical ultrasound examinations at 15 and 22 weeks' gestation were normal. Ultrasound examination revealed that the fetal bowel echogenicity was not prominent. Attention was directed to an abnormal course of the right and left hepatic veins (Figure 1). Color Doppler imaging revealed a shunt between the inferior left portal vein and the left hepatic vein (Figure 2a, Videoclip S1), and another shunt between the medial left portal vein and the right hepatic vein (Figure 2b, Videoclip S2). In addition, the ductus venosus was absent. Three-dimensional static high-definition flow imaging was used to display the two intrahepatic shunts (Figure 3). The splenic vein and the main portal vein were observed as having a normal course (Figure 4, Videoclip S3) with no sign of extrahepatic shunt. Given that the liver was bypassed by the two shunts, sonographic follow-up focused on signs of strain on the right side of the heart. Examination showed a larger atrium and ventricle on the right than the left side of the heart, ‘ballooning’ of the foramen ovale towards the left atrial wall, pericardial effusion and pleural effusion. Analysis of right atrial function revealed increased fetal tricuspid annular plane systolic excursion. In addition, dilation of both the inferior and superior vena cavae was detected. These signs were manifested in a mild and non-deteriorating pattern. The parents were invited for genetic consultation, but they declined further investigations, including late amniocentesis for chromosomal microarray analysis. Fetal heart monitoring and biophysical profile were normal throughout the remainder of follow-up. At 38 weeks' gestation, owing to onset of growth restriction, a decision was taken to induce labor. Birth weight was 2750 g. Except for slightly high blood ammonia levels (140 µg/dL, which decreased to 90 µg/dL in the following weeks), the neonate's condition was good in the days following delivery. Ultrasound examination on day 6 depicted a shunt between the left hepatic vein and a branch arising from the left portal vein, and another shunt between the portal vein and the middle hepatic vein (Figure 5). In conclusion, we have described a rare anomaly of two intrahepatic portosystemic shunts associated with absence of the ductus venosus, that was detected prenatally. When CPSS is diagnosed prenatally, detailed scanning for additional, mainly cardiovascular, anomalies should be performed1, 2. Prenatal diagnosis of CPSS is important because genetic counseling can be offered before labor, and follow-up can be initiated immediately after delivery. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.