Reconstruction of the main portal vein for a large saccular aneurysm

Abstract

Background

A large aneurysm of the main portal vein is rare, and the appropriate surgical procedure is uncertain. Reconstruction of a main portal vein affected by a large saccular aneurysm is described.

Case outline

Abdominal pain led to the diagnosis of a large saccular aneurysm of the main portal vein in a 58-year-old woman who had undergone cholecystectomy 10 years earlier. At laparotomy a dorsolateral approach to the hepatoduodenal ligament was performed with no attempt at extensive separate exposure of the anatomical structures in the hepatoduodenal ligament, so as to avoid the devascularisation of the common hepatic duct and additional weakening of the portal vein wall. The aneurysm was longitudinally incised, and the portal vein was reconstructed from the walls of the aneurysm with a longitudinal running suture. The rest of the aneurysmal wall was wrapped around the portal vein, leaving it normal in size and contour. Recovery was uneventful. Follow-up CT scan showed a patent portal vein in the region of the former aneurysm.

Discussion

Large saccular aneurysms can rupture, bleed and cause death. The potential hazards of manipulation of large portal vein aneurysms are negligible in comparison with the possible complications of the aneurysm itself. In our opinion the ease with which the main portal vein was dissected and reconstructed make an elective operation in such cases a reasonable approach.

Introduction

Venous aneurysms, including portal vein aneurysms, are rarely encountered in clinical practice ¹. Since Barzilai and Kleckner's report ² in 1965 fewer than 30 cases of portal vein aneurysm have been reported in the literature, including less than 20 cases with the aneurysm involving the extrahepatic portal vein ³. Fusiform aneurysms are more common than saccular aneurysms, but saccular aneurysms are more likely to develop complications ⁴. However, the rarity of portal vein aneurysms has obscured their natural history, thus making it difficult to predict outcome when they are managed by observation alone. It is even more difficult to choose the appropriate operative procedure (when indicated), as only anecdotal information is available ³, which deals primarily with the complications of the aneurysm itself (rupture, thrombosis) ²,⁵,⁶. This article reports the reconstruction of the main portal vein affected by a large saccular aneurysm.

Case report

A 58-year-old woman with abdominal pain, nausea and vomiting was admitted to hospital. She had undergone cholecystectomy for gallbladder stones 10 years previously. There was no history of jaundice, haematemesis, melaena, abdominal inflammation or trauma. No abdominal mass was palpated. Liver function study tests were normal. Ultrasound scan showed a 5.0×5.0×4.5 cm well-circumscribed anechoic structure at the main trunk of the portal vein, compressing the inferior vena cava. It was believed to be a portal vein aneurysm. Helical CT was performed to confirm this rare diagnosis. Enhancement of the anechoic structure by intravenous contrast material, and 3-D reconstruction showed a large saccular aneurysm located in the main trunk of the portal vein (Figure 1).

Figure 1. .

3-D reconstruction shows a large saccular aneurysm located in the main trunk of the portal vein.

In the presence of non-specific gastrointestinal symptoms and absence of liver disease it was difficult to decide whether this woman's aneurysm should be observed or surgically corrected. The decision to operate was made on the basis of previous post-cholecystectomy ultrasound findings, which showed a normal diameter portal vein. Since the aneurysm was unstable and expanding, there was a risk of thrombosis or rupture.

Through a modified right subcostal incision the duodenum was mobilised to the midline, bringing the lateral and dorsal surface of the aneurysm into view. There was no surrounding inflammation (Figure 2). Intravenous heparin (5000 IE units) was given. After proximal and distal vascular control was obtained by double-looping the hepatoduodenal ligament with a silastic loop, the aneurysm was cautiously mobilised because its wall was extremely thin. There was no attempt to carry out extensive exposure of anatomical structures in the hepatoduodenal ligament so as to avoid additional weakening of the portal vein wall and devascularisation of the common hepatic duct. For the same reason there was no attempt to compress the aneurysm between the common bile duct and hepatic artery, as previously advised ³. The aneurysm was longitudinally incised and the portal vein was reconstructed from the walls of the aneurysm with a longitudinal running suture on the intraluminal surface of the vessel. The rest of the aneurysmal wall was laterally wrapped around the portal vein, leaving it normal in size and contour (Figure 3). The patient has remained asymptomatic for 6 months. Follow-up CT scan showed a patent portal vein in the region of the former aneurysm (Figure 4).

Figure 2. .

Operative photograph showing the portal vein aneurysm.

Figure 3. .

Surgical technique for reconstructing the portal vein aneurysm. (a) The vessel is controlled by loops on either side of the aneurysm. (b) The aneurysm has been sutured longitudinally to reduce its diameter, (c) The aneurismal wall is wrapped around the reconstructed portal vein, (d) Cross-sectional diagram showing the reconstructed portal vein lying behind the bile duct (yellow) and hepatic artery (red).

Figure 4. .

Post-operative CT shows a patent portal vein.

Discussion

Portal vein aneurysm can be defined as a localised dilatation of the portal vein beyond normal limits ⁷ and can be divided into extrahepatic and intrahepatic types. The aetiology of portal vein aneurysms is controversial. Some researchers suspect a congenital cause ⁸. Others speculate that it is caused by portal hypertension ⁹. Presumably acquired causes such as trauma and pancreatitis have also been described ¹⁰. We speculate that in the present case the main cause may have been an acquired weakness of the vessel wall after gallbladder surgery. The surgeon who performed the operation described it as difficult, but he did not report any morphological changes of the portal vein. Normal ultrasound examinations in the early years after that operation suggest the slow expansion of the saccular aneurysm.

Most venous aneurysms are not life-threatening, but popliteal venous aneurysms are notorious for their propensity to thrombose. Intrahepatic portal vein aneurysms and small fusiform extrahepatic aneurysms (which are commoner than saccular aneurysms) rarely give rise to complications and may be managed by regular observation alone ⁴,⁹. Evidence from small series has shown that larger saccular aneurysms of the extrahepatic portal vein often develop thrombosis and lead to portal hypertension ⁹. They can even rupture, bleed and cause death ²,⁶. The potential hazards of manipulation of a portal vein aneurysm are negligible in comparison with the possible complications of the aneurysm itself ³. In our opinion, the ease with which the main portal vein was dissected and reconstructed make an elective operation in such cases a reasonable approach.

We believe that there is no need for extensive separate exposure of the anatomical structures in the hepatoduodenal ligament, which would risk possible devascularisation of the common hepatic duct and additional weakening of the exposed surfaces of the main portal vein. For the same reason there is also no need to compress the aneurysm between the common bile duct and the hepatic artery. The aneurysm can easily be approached from the dorsolateral aspect and reconstructed. The dissected and potentially weak areas of the main portal vein are then covered with the remains of the aneurysmal wall. The technique is safe and reduces the possibility of damage to the main portal vein and other structures in the hepatoduodenal ligament.