Case studyAbernethy malformation type II with nephrotic syndrome and other multisystemic presentation: an illustrative case for understanding pathogenesis of extrahepatic complication of congenital portosystemic shunt
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].
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Case report
An 18-year-old woman of Filipino decent, who had initially been managed conservatively for nephrotic syndrome following a root canal infection 4 months prior at another institution, presented to us with new onset fatigue, shortness of breath, dry cough, and intermittent fevers over 2 weeks. Urine microscopy showed 3+ blood, and proteinuria was quantitated at 2.6 g/d. Complement levels were normal, and autoimmune/viral serologies, negative. Serum albumin was 20 g/L, and creatinine was initially
Discussion
Although overall a rare malformation, congenital extrahepatic P-S shunts are being diagnosed more frequently with the advances in imaging techniques, especially in the perinatal periods following directed screening exercises [10]. Abernethy P-S malformation in adulthood [10], [11] is an even rarer occurrence and may represent a “milder” disease variant, especially because most of these are type II (ie, partial shunt with presence of a hypoplastic branch of the portal vein) compared with type I
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