Congenital double intrahepatic portosystemic shunt: Imaging findings and endovascular closure.

A 3-month-old boy, first child of unrelated parents, born by emergency Caesarean section at the thirty-first week of pregnancy because of heart failure and fetal hydrops, prenatal screening of mitral valve dysplasia and ostium secundum type atrial septal defect, was admitted to the Gastroenterology Hepatology and Nutrition Unit of the hospital for high blood ammonia levels [159 micrograms/decilitre (μg/dL); normal levels: 0-75 μg/dL]. At admission, the patient was in good clinical condition, without encephalopathy or heart failure signs. Liver function tests were in the normal range as well as blood gas analysis. The patient underwent a wide metabolic screening in order to identify specific diagnosis. All the investigations were negative while his ammonia level was repeatedly high. Therefore, he was started on oral Arginine (250 mg/kg/day in 3 doses) with prompt resolution of hyperammonemia. As part of the diagnostic work-up a liver ultrasound (US) examination was performed and showed a communication channel between the left portal vein and the inferior vena cava suggesting a persistent patent ductus venosus (PDV) (Figure 1A). No focal hepatic lesion was detected. Contrast-enhanced (CE) multidetector-row computed tomography (MDCT) of the liver confirmed the PDV arising from the hypertrophic umbilical segment of the left portal vein to join the subdiaphragmatic tract of inferior vena cava. The right portal vein appeared very hypoplastic while intrahepatic portal vessels were poorly detected. Moreover, an additional smaller intrahepatic shunt between the right portal system and the posterior subdiaphragmatic inferior vena cava was also visualized (Figure 1B-1D). A diagnosis of congenital portosystemic shunt was made and the cause of hyperammonemia was finally attributed to portal flow bypassing the liver through the shunt. A 12 months clinical follow up was carried out waiting for a spontaneous regression of the shunt. Clinically the follow up was uneventful with the patient thriving well and developing fine. Ammonia levels remained within the normal range. However the strict correlation between shunt patency and elevated blood ammonia warned off reducing medical treatment because of the risk of brain toxicity and portal systemic encephalopathy.1,2 Doppler US scan confirmed shunt patency, therefore its closure was considered to prevent complications. Transjugular portography with balloon occlusion test of the PDV was performed (Figure 2). Angiography revealed a higher flow in portal system through the bigger shunt with portal pressure value of 11 mmHg. No intrahepatic portal branches were visualized. The smaller fistula arose from the right hypoplastic portal vein and flowed with Y shape into the subdiaphragmatic inferior vena cava (Figures 2A and 2B). Occlusion test with a 10 mm diameter Swan-Ganz catheter balloon inflated within the ductus allowed visualization of the entire intrahepatic portal vessels without increased portal pressure (17 mmHg) (Figures 2C and 2D). Endovascular closure of the double portocaval shunt was performed in one step (Figures 3A and 3C). Coil embolization was performed first in the smaller shunt while an Amplatzer septal occluder device was released in the PDV. The malformations appeared closed and the portal vascularization increased particularly in the right system. Plasma ammonia levels spontaneously decreased soon after the procedure (21 μg/dL) so medical therapy with arginine was suspended. After