In 1793, John Abernethy1 published a report of a portal venous malformation discovered during a postmortem examination of a 10-month-old girl. The malformation consisted of termination of the portal vein in the inferior caval vein at the level of renal veins, with absence of the intrahepatic portal veins. She also had multiple spleens, right-sided heart, and right aortic arch. In honour of his original description, congenital extrahepatic porto-systemic anastomoses are now known as Abernethy malformations. These malformations are very rare, as far as we can establish with less than 100 cases having been reported in the literature. In some patients, there is complete absence of the intrahepatic portal vein, and there is an obligatory end-to-side porto-systemic venous anastomosis. In other patients, the intrahepatic portal veins are present, and there is a side-to-side porto-systemic anastomosis. The end-to-side anastomoses are reported more frequently than the side-to-side variants.
We report here a child who had tricuspid atresia in association with complete absence of portal vein, and an end-to-side porto-systemic anastomosis. Tricuspid atresia itself is a relatively uncommon defect, being found in fewer than 3% of patients with congenital cardiac malformations. Cardiac anomalies have previously been described in association with the Abernethy malformation,2 but to the best of our knowledge, ours is the first case in which tricuspid atresia accompanies the anomaly of the portal venous system.
Case report
The patient is a female, born at 36 weeks, and the product of artificial insemination. Her cardiac defect was diagnosed prenatally, and confirmed by postnatal echocardiography. The heart was left-sided heart, with usual arrangement of the atrial appendages, and bilateral superior caval veins, with left superior caval vein draining into the right atrium through the coronary sinus. There was a moderate sized defect across the oval fossa. The right atrioventricular connection was absent, and the right ventricle was incomplete and severely hypoplastic, being fed through a muscular ventricular septal defect of moderate size. The great arteries were normally related. The ventricular septal defect became restrictive over time, and the main source of flow of blood to the lungs was through the large patent arterial duct. Since there was a good balance between pulmonary and systemic flows, no neonatal interventions were performed. The child underwent an elective bilateral bidirectional Glenn procedure at 3 months of life and recovered uneventfully.
The Abernethy malformation has been identified during abdominal ultrasonography performed at 5 days of age. The intrahepatic portal veins were absent, the splenic and mesenteric veins joining together to drain into the inferior caval vein. A magnetic resonance imaging of the abdomen confirmed the diagnosis (Fig. 1). Initial liver function tests showed mildly elevation of direct bilirubin, at 1.6, with total bilirubin measured at 7.7, and normal liver enzymes. The levels of ammonia, and clotting studies, were within normal limits, and the jaundice resolved.
Figure 1. Magnetic resonance imaging of the abdomen showing the porto-systemic anastomosis. The splenic vein (SV) joins the superior mesenteric vein (SMV) and drains directly into the inferior caval vein (ICV).
Other congenital abnormalities, and health problems, included minor sacral anomalies identified on abdominal X-ray and vesico-ureteral reflux requiring antibiotic prophylaxis against infections of the urinary tract.
Discussion
Embryologically, the portal veins are derived from selective involution and persistence of certain vitelline venous structures. The embryology of the inferior caval vein is complex, and it is derived from several venous channels. This complex development of the inferior caval vein, and its close relation with the vitelline venous system, may explain the development of the porto-systemic venous anastomoses seen in the Abernethy malformation.
Massin et al.,2 in 1999, carried out a systematic review of cardiac anomalies present in congenital absence of portal vein with end-to-side porto-systemic anastomosis, reporting cases of atrial septal defect, ventricular septal defect, aortic stenosis, pulmonary stenosis, coarctation of aorta and patency of the arterial duct. Some of these patients also had multiple spleens and right-sided hearts. We further reviewed the literature for other cardiac abnormalities in the setting of the Abernethy malformation and other portal venous malformations. The results are summarized in Table 1. In a review of children with Down's syndrome, three children had an atrioventricular septal defect and congenital absence of intrahepatic portal veins.3 Cardiac defects are reportedly rare in patients with side-to-side porto-systemic anastomosis. Hypoplastic left heart syndrome, pulmonary atresia, and patent arterial duct have been described in individual patients with this variant.4–6
Table 1. Reported cardiac defects in various portal venous anomalies.
A variety of cardiac anomalies have also been described in other defects of the portal venous system (Table 1). Congenital absence of the venous duct has been associated with Down's, Noonan's, and Turner's syndromes.7 Portal venous atresia with portal hypertension has been reported in two cases with tetralogy of Fallot.8
In a review of 61 reported cases with extrahepatic porto-systemic anastomoses,9 congenital cardiac lesions were present in one-third of the cases, with nearly one-fifth being associated with the finding of multiple spleens. Skeletal anomalies were present in one-tenth of the patients.
Alteration of normal portal venous flow has been speculated to play a role in the pathogenesis of certain cardiac defects.2 The wide spectrum of malformations described in this review, however, is unlikely to be explained solely by the alteration in portal venous flow, and there are probably multiple mechanisms responsible for this rare association.
The Abernethy malformation itself can be asymptomatic, or can present in a variety of ways. Some patients present acutely with hepatic encephalopathy, and in others, the presentation may be insidious, with eventual presentation as delayed mentation at an older age. Toxic substances produced during digestion are normally metabolized by the liver. In Abernethy malformation, some or all of these metabolites bypass the liver and directly reach the systemic circulation. Elevated levels of ammonia, and deposition of heavy metals over long periods of time, have been assumed to cause progressive cerebral atrophy in these patients.
These patients can also develop hepatic nodules and they are at high risk for developing hepatocellular carcinoma.6 Two patients with porto-systemic anastomoses were reported to have primary pulmonary hypertension.9, 10 It is speculated that pulmonary hypertension in these patients is secondary to some of the toxic metabolites from the portal circulation directly reaching the systemic circulation.
Monitoring the levels of ammonia in the serum over time, ensuring adequate hydration during times of acute illness to prevent hyperammonemia, and periodic screening to detect hepatic tumours, are reasonable precautionary measures. Hepatic transplantation, and division of the porto-systemic shunt, has been done in these patients with variable success.5
In patients with Abernethy malformation, the portal venous abnormality itself may not cause symptoms in childhood. Hence, it is possible that this malformation is under-diagnosed in children with congenital cardiac defects, and its incidence may be higher than what appears in the literature. Moreover, with improvement in the treatment of cardiac defects, many of these patients will survive into adulthood. This association should be kept in mind while encountering unexplained neurological symptoms and pulmonary hypertension in patients with history of corrected congenital cardiac disease. It may also be reasonable to consider cardiac screening in children with anomalies of the portal vein.
