Application of the "five-plane method" for the prenatal diagnosis of fetal extrahepatic portosystemic shunts: a retrospective cohort pilot study.

Background: A congenital extrahepatic portosystemic shunt (CEPS) is a rare condition. Currently, CEPS is primarily diagnosed in the postnatal period. Most cases are detected using imaging techniques such as computed tomography (CT), digital subtraction angiography (DSA), and magnetic resonance imaging (MRI), typically after severe complications arise. Due to the effect of abdominal intestinal gas, the diagnosis of CEPS via postnatal ultrasound is relatively challenging. Conversely, prenatal ultrasound offers a distinct advantage in the diagnosis of CEPS. However, a lack of understanding of this condition often leads to missed diagnoses. This study aimed to introduce the "five-plane method" to enhance the detection of CEPS using prenatal ultrasound, and to evaluate the feasibility of this method in evaluating the development of the fetal intrahepatic system and extrahepatic portal venous system (EHPVS). Methods: This retrospective cohort study enrolled all fetuses referred to a single center in China for suspected CEPSs between January 2017 and December 2023. The fetuses were scanned using the "five-plane method", which employs high-definition flow imaging (HDFI) of the fetal abdomen across four transverse planes and one coronal plane. This method enables the visualization of the intrahepatic portal venous system (IHPVS), the ductus venosus (DV), and the hepatic venous system, and the confluence of the main portal vein (MPV) with the portal sinus (PS), as well as the junction at which the superior mesenteric vein (SMV) and the splenic vein (SV) merge into the MPV. The origin of the shunting vessels was identified using the "five-plane method". Subsequently, HDFI was used to track the drainage vein of the CEPS, and it was classified according to Kobayashi's criteria. Postnatally, the diagnosis and type of CEPS were confirmed through surgical examination, radiographic studies, and/or postmortem autopsy. Results: Five fetuses were diagnosed prenatally with CEPS. The shunt vessels of the five fetuses originated from the PS and the main trunk of the portal vein (PV). The four live-born infants exhibited different types of shunts (of which, two were classified as Type A and two as Type B). All four had well-developed PVs and normal cardiac function. Postnatally, two infants underwent ligation of the shunt vessels, while the other two infants received percutaneous shunt treatment. All four infants had favorable prognoses, with follow-up periods ranging from 1 year and 3 months to 5 years. The terminated case, classified as Type C, showed poorly developed SV and MPV, but well-developed intrahepatic PVs, as confirmed by autopsy. Postnatal evaluation confirmed complete concordance with the prenatal diagnoses in all five cases, resulting in a sensitivity and specificity of 100%. Conclusions: The five-plane method can be used to identify the origins of abnormal extrahepatic shunting vessels, and assess the development of the IHPVS before birth. This may aid in genetic counseling and in predicting the prognosis of affected fetuses.