Abernethy malformation type II with nephrotic syndrome and other multisystemic presentation: an illustrative case for understanding pathogenesis of extrahepatic complication of congenital portosystemic shunt

Summary

Abernethy malformation, an extrahepatic congenital portosystemic shunt, is more often diagnosed based on associated cardiac or pulmonary malformation. Although predominately a pediatric diagnosis, “late diagnoses” in adulthood have been reported especially in type II malformations that involve only a partial shunt of portal circulation directly into the inferior vena cava. Aside from the cardiac-related presentation, Abernethy malformation is also associated with multiple liver nodules, either benign or malignant, and pulmonary hypertension. In this report, we present immunoglobulin A glomerulonephritis with nephrotic syndrome as a hitherto unrecognized manifestation of this malformation outside the pediatric population, in a patient who also had pulmonary hypertension and multiple liver tumors. We also propose a pathogenetic basis for this multisystemic presentation that includes release into the systemic circulation of unfiltered bacteria, vasoactive substances, and immunoglobulin A–antigen complexes.

Introduction

Congenital extrahepatic portosystemic (P-S) shunts are a rare anomaly of the splanchnic vasculature in which portal venous blood is diverted into systemic veins, most commonly the inferior vena cava (IVC); this malformation is also known as the Abernethy malformation, in recognition of its original description. Abernethy malformations are further subclassified into 2 groups: types I and II. Type I is characterized by a complete absence of the extrahepatic portal vein, leading to diversion of what would have been portal blood (from superior mesenteric and splenic veins) into the IVC. Type II, on the other hand, consists of a hypoplastic portal vein supplying the liver with a side-to-side anastomosis with a larger branch that drains directly into the IVC, producing only a partial portal venous flow into the liver [1]. Type I is further subclassified into Ia and Ib based on the absence or presence of a patent connection between the superior mesenteric vein and the splenic vein, respectively [1]. Other variations of P-S shunts have been reported. For example, Mistinova et al [2] reported a case in which abdominal venous blood drained into the suprarenal IVC via the left renal vein and dilated left gastric veins. Embryologically, Abernethy malformation can most easily be explained by a failure of the vitelline veins to establish anastomosis with the umbilical veins during early gestation [3].

The clinical manifestations of Abernethy malformation are broad, ranging from entirely asymptomatic patients [4] to hepatic or systemic sequelae of P-S shunting, such as pulmonary hypertension; hepatopulmonary syndrome; hepatic encephalopathy; or multiple liver nodules/tumors, including focal nodular hyperplasia (FNH), nodular regenerative hyperplasia, hepatocellular adenomas, and hepatocellular carcinomas (HCCs) [5], [6], [7]. Associated cardiac anomalies are present in approximately one-third of patients and include ventricular and atrial septal defects, patent ductus arteriosus and foramen ovale, tricuspid atresia, and congenital hypertrophic cardiomyopathy [4]. Apart from a single report in the pediatric population [8], congenital P-S shunts are not well recognized as a cause of glomerulonephritis and even less well correlated with the nephrotic syndrome, although these complications are better appreciated in cirrhotic patients with therapeutic construction of portacaval shunts for portal hypertension [9].