Abernethy malformation with portal vein aneurysm in a child.

Abernethy malformation is an extremely rare anomaly of the splanchnic venous system. We describe multidetector computed tomography findings of an incidentally detected Abernethy malformation with portal vein aneurysm in a two-and-half-year old child. The computed tomography scan was performed for the evaluation of respiratory distress, poor growth, and loss of appetite.

INTRODUCTION

Abernethy malformation was first reported by John Abernethy in 1793.[1] Abernethy malformation is an extremely rare anomaly of the splanchnic venous system. It is characterized by the diversion of portal venous blood away from the liver, by either end-to-side or side-to-side shunt.

CASE REPORT

A two-and-half-year-old child presented with respiratory distress, poor growth, and loss of appetite for 2 months. His liver enzymes, bilirubin level, and serum proteins were normal. The patient was referred for evaluation of respiratory distress and loss of appetite.

Computed tomography (CT) showed mild cardiomegaly with collapse/consolidation of bilateral lung lobes. Incidentally, there was the presence of an end-to-side shunt between the right branch portal vein (PV) and the inferior vena cava (IVC) with fusiform aneurysmal dilatation of the PV continuing into the left branch, which abruptly ended after a short distance. There was aplasia of the right branch of the PV [Figures 1 and 2]. Distal branches of the PV were not seen. The tributaries of the hepatic veins were seen. The hepatic artery appeared normal. The splenic and superior mesenteric veins had normal orientation, and these vessels joined to form the main PV. A diagnosis of congenital extrahepatic portocaval shunt (CEPS) (Abernethy malformation type 1) with PV aneurysm was made. Since the patient was asymptomatic and liver enzymes were normal, the patient was advised follow-up.

Figure 1

(a and b) Axial CT scan. There was the presence of end-to-side shunt between the right branch of PV and the IVC (solid thick arrow), fusiform aneurysmal dilatation of the PV, which was continuing into the left branch (thin arrow)

Figure 2

Coronal multiplanar reconstruction (MPR) shows the presence of end-to-side shunt between the right branch PV and the IVC (b) (arrow) with fusiform aneurysmal dilatation of the PV (a).

DISCUSSION

The portal venous system and IVC develop between the 4th and 10th weeks of embryonic life by selective apoptosis of some portions of the vitelline, which may lead to the potential for congenital portosystemic shunts.[2] Morgan and Superina classified CEPS into two types.[3] Type I CEPS (congenital absence of the PV) is an end-to-side shunt between PV and the systemic circulation. Here all the splanchnic venous return enters the systemic circulation, and the liver is not perfused with portal venous blood at all. Type II CEPS is a partial side-to-side shunt between the portal and systemic vein, where only a fraction of the splanchnic venous return bypasses the liver parenchyma. These are rarer with no sex preference.

CEPS are also associated with an increased frequency of hepatic neoplasms.[3-7] It has been proposed that the diversion of hepatotropic substances in the splanchnic venous blood, such as insulin and glucagon, away from the liver results in alterations of development, function, and regenerative capacity of the liver. This diversion, along with increased arterial hepatic flow, may contribute to the development of hepatic neoplasms.[8] Long-term follow-up and monitoring are recommended for these patients. However, in our patient, the liver was normal.

Currently, a diagnosis of Abernethy malformation is usually made by noninvasive cross-sectional imaging techniques such as ultrasound, CT, or MRI, which show the shunt and any intrahepatic PV branches. However, liver biopsy may be necessary in patients with suspected type 1 malformation since an occasional patient may have small PV radicles which cannot be seen on ultrasound but can be observed on liver biopsy.[2]

PV aneurysm is a rare clinical entity having a focal fusiform or saccular dilatation of more than 20 mm.[9] Aneurysms of the PV may occur either proximally at the junction of the superior mesenteric vein and splenic vein or more distally in the PV radicals. The etiology of PV aneurysms is controversial. Congenital origin is suggested based on the discovery of variations in the embryologic development of the PV and may be associated with multiple vascular malformations. The origin of acquired PV aneurysms is more commonly secondary to cirrhosis and other hepatic diseases. Pancreatitis can be included as an extrahepatic cause. In the majority of cases, patients are clinically asymptomatic. The majority of patients with Abernethy malformation have other associated anomalies such as liver and cardiac abnormalities. Kumar et al. described a case of 24-year-old man having CEPS type-2 with PV aneurysm during an investigation for nonspecific abdominal pain.[5]

Determining the type of shunt is particularly important in the planning of treatment. The patients with type I malformation need clinical, biochemical, and imaging follow-up. However, those patients with type 2 malformations need surgery or percutaneous transcatheter coil placement.[7]

In conclusion, although CEPS is a rare anomaly, it must be recognized early to prevent the consequences of metabolic derangements by appropriate surgical treatments. Imaging plays a vital role in the diagnosis of CEPS. In many cases, the detection of tiny intrahepatic portal venous radicals may be beyond the resolution limits of the available imaging methods. The limitation of imaging in determining the type of shunt in some cases should be recognized, and a histopathological confirmation of the type of shunt may be crucial in deciding the treatment course.