Discussion
Abernethy malformation is a congenital portal vein malformation caused by abnormal selective preservation and degeneration of the peri-intestinal yolk vein plexus during the formation of the portal vein system during the embryonic period1. The disease is rare, affecting an estimated 1/30000 live births7,9. Various degrees of preservation and degeneration lead to diverse vascular variations2. In 1994, Morgan et al. divided Abernethy malformation into two types: Type I, characterized by intrahepatic portal vein complete loss and complete side-to-side shunt; and Type II, characterized by the presence of intrahepatic portal vein and partial side-to-side shunt10. Depending on the confluence of the superior mesenteric vein and the splenic vein, Type 1 Abernethy malformation can be subsided into two types. Type 1 is more common than Type 28. In our case, the intrahepatic vein was present, and there was an extensive shunt between the hepatic portal vein and the inferior vena cava. Type II Abernethy malformation was identified.
The clinical manifestations of Abernethy deformity differ depending on the location of the abnormal shunt vessels and combined malformations, which are divided into three classes11: (1) abnormal liver function, liver fatty change, and severe cases such as a regenerative nodule or tumor formation caused by insufficient liver bloody supply11; (2) symptoms related to shunt, including hyperammonemia, hypergalactosemia, hepatic encephalopathy, liver lung syndrome, pulmonary hypertension, heart failure, and gastrointestinal bleeding12,13; (3) symptoms associated with coexisting congenital abnormalities such as congenital heart disease7. Zhang et al. reported 12 children with Abernethy malformation, nine of whom presented with hematochezia, and all had abnormally thick inferior mesenteric vein entering the inferior vena cava through the iliac vein in the pelvic cavity5. Other less common symptoms include abnormal liver transaminase, jaundice, and hypoxemia5. Abnormal laboratory tests are usually caused by untreated portal vein blood entering the vena cava system and include elevated serum ammonia and bile acids. Patients with Abernethy malformation and congenital heart diseases may initially present with symptoms related to cardiac dysfunction7. In the present case, total bile acids and total bilirubin decreased significantly after portal shunt ligation.
Abernethy’s deformity is rare but often associated with other malformations. Congenital heart disease is one of the most common associated malformations. Mistinova et al. reviewed 84 cases with congenital absence of the portal vein and found that 65% were female, and 22% had heart disease1. Christiane et al. reviewed the characteristics of 316 patients with a congenital portosystemic shunt in the literature and found that the percentage of patients associated with heart disease was also 22%4. Patients with cardiac disease are more common in Type 1 than Type 2 (68% vs. 32%)4. The most common type is a ventricular septal defect, followed by atrial septal defect, patent ductus arteriosus, atrioventricular septal defect, and coarctation4. In the present case, we reported a patient with Type 2 Abernethy malformation and MAPCAs, which is not found in the literature. Congenital MAPCAs can be associated with or without heart defects. Those with heart defects tend to have cyanotic defects. MAPCAS without cyanotic congenital heart defects are rare and are associated with premature birth, lung tissue infection, and pulmonary dysplasia14. Our patient was born at term and had no other heart defects. In another study, the authors found that 27.4% of patients with congenital portosystemic shunts had cardiac disease7.
The co-existence of Abernethy malformation and cardiac raises the suspicion that these two diseases might be related. Some authors suggested that abnormal hemodynamics might cause the abnormal persistence of an embryonic vitelline vein1, while other authors held that portosystemic shunts might cause a “congestive effect” and the heart defects would result from adaptive change15. In some cases with multiple cardiovascular diseases, angiogenesis might play a more critical role16. Nevertheless, there is no definitive explanation for the relationship between these diseases; further research is needed.
In addition to cardiovascular anomalies, other deformities may be associated with Abernethy malformation. A small number of patients are affected by Turner syndrome, Caroli syndrome, Goldenhar syndrome, and Down syndrome8. The child in our case was incidentally found to have Dandy-Walker syndrome (revealed by a head CT performed after a traumatic brain injury). Before that time, no neurological abnormalities were found. Other deformities may be found in the urinary and male genital tract, the spleen, brain, and skeletal system1. More than 40% of patients with Abernethy malformation may have hepatic lesions such as focal nodular hyperplasia, adenoma, hepatocellular carcinoma, and cirrhosis1,8. The relationship between these two diseases might involve absent or decreased portal vein flow and the contemporaneous increased supply of the hepatic artery8. There was no hepatic lesion in our case before surgery and during follow-up. However, the follow-up was relatively short, and additional attention should be paid to hepatic lesions in the future.