Teaching Case

We present a case of a 15-year-old boy whose blood testing revealed an increase in liver parameters, including direct bilirubin and transaminases. Physical exam and history were otherwise unremarkable.

An abdominal ultrasound was performed, revealing the presence of a vascular abnormality, consisting of a shunt from the portal vein directly to the inferior vena cava (Fig. 1a/1b). The liver echostructure was slightly heterogeneous with several, well-defined, round nodules (Fig.1c). Abdominal CT and liver MR were performed for further characterization, confirming the presence of the anomalous venous shunt (Fig.2) and the liver nodules (Fig. 3). The two largest nodules depicted a T2-hyperintense central area, compatible with a scar and a surrounding slightly T1-hypointense signal. In the dynamic study, there was mild and progressive contrast uptake with homogenous, complete filling of all nodules in the equilibrium phase (Fig. 4). 

Abernethy malformations are rare vascular anomalies of the splanchnic venous system. They consist of congenital portosystemic shunts and result from the persistence of the embryonic vessels. There are two types of Abernethy malformations. Type I consists of an end-to-end shunt. In this type, there is an absence of portal vein, and systemic blood flows directly to the vena cava. Type II consists of a side-to-end shunt with partial liver perfusion with portal blood [1].

Although some patients may be asymptomatic at the time of diagnosis, as our patient was, complications of Abernethy malformations may include increased serum ammonia, hepatic encephalopathy, or hepatocellular carcinoma (HCC) [2].

There is an ongoing debate on why patients with congenital portosystemic shunts have a much higher risk of developing liver nodules, particularly regenerative hyperplastic nodules. Hyperplastic or regenerative nodules are well-defined regions of normal liver parenchyma that have enlarged in response to a stimulus such as necrosis or as in this case, a vascular one [3]. Patients with significant portal venous deprivation have a compensatory increase in hepatic arterial flow to supply the liver. On the other hand, exposure to different saturations of oxygen [4] and even the differences in the concentration of metabolites that go through a first pass in the liver may also trigger the appearance of the nodules [5].

In this case, imaging played a fundamental role. On the one hand, it was possible to accurately map the shunt and reveal the presence of a portal vein without intrahepatic branching. On the other hand, and in this case, MR in particular, permitted the characterization of the hepatic nodules.

Considering the imaging features, particularly the presence of a central scar and the low enhancement should lead to the hypothesis of a regenerative hyperplastic nodule. However, dysplastic nodules display some overlapping imaging features, particularly the lack of a obvious arterial enhancement [6]. For this reason, liver biopsy was performed and confirmed the diagnosis of a regenerative hyperplastic nodule. Other types of tumors that can arise in the case of Abernethy malformation, including hepatoblastoma and HCC, should also be included on the list of differentials [7].

Written informed patient consent for publication has been obtained.