LAUSR

A 72-year-old woman who underwent segment 6 hepatectomy for a hepatocellular carcinoma on a background of hepatitis C virus-related chronic hepatitis 6 years ago was referred to our hospital with a superior mesenteric venous aneurysm (SMVA) that was incidentally detected by computed tomography (CT) for hepatocellular carcinoma surveillance. A contrast-enhanced CT revealed a saccular aneurysm in the superior mesenteric vein which was gradually increasing in size from 11 to 23 mm over the course of 4 years. Laboratory investigation revealed no significant abnormalities, including antinuclear antibody levels, to suggest collagen disease or vasculitis. Abdominal CT (Fig. 1a) and three-dimensional CT angiography (Fig. 1b) revealed a saccular aneurysm measuring 23 mm in diameter located on the dorsal side of superior mesenteric vein (SMV), approximately 10 mm before its confluence with the splenic vein; there was no evidence of splenomegaly, gastrorenal shunt, ascites, portal thrombosis, or other abdominal venous aneurysms. The digital subtraction arterial portography showed a saccular aneurysm at the confluence of SMVand first jejunal vein (Fig. 1c). The aneurysm was asymptomatic but exhibited a tendency for expansion; therefore, coil embolization was performed to prevent rupture. A percutaneous transhepatic approach was adopted by puncturing the right posterior portal vein under ultrasonographic guidance. A 5-Fr sheath and a 4-Fr diagnostic catheter (Multipurpose; Medikit, Miyazaki, Japan) were placed in the SMV. A 2.7-Fr microcatheter (ProgreatΩ; Terumo, Tokyo, Japan) was inserted into the aneurysm with a 0.014-in guidewire (Synchro2, Stryker, West Valley City, UT, USA) (Fig. 2a). Next, the aneurysmal sac was packed with detachable coils (Ruby coils; Penumbra, Alameda, CA, USA, and Azur coils; Terumo), while maintaining SMV patency. Digital subtraction portography after coil embolization showed the disappearance of blood flow inside the aneurysm and good patency and blood flow of the SMV (Fig. 2b). The patient had no symptoms and was discharged 10 days after the procedure. Follow-up contrast-enhanced CT performed 6 months after the procedure showed no evidence of aneurysmal recurrence, portal vein thrombosis, or other significant abnormalities. Aneurysms of the portal venous system are rare clinical entities, comprising 3% of all venous aneurysms. SMVA is an extremely rare presentation first described in 1982, with a few over a dozen cases reported to date. Albeit unclear, congenital and acquired origins are considered as the two main etiologies of aneurysms of the portal venous system. Potential complications are symptomatic disease including portal hypertension, thrombosis, and bleeding due to rupture. Although the need for treatment of SMVA remains controversial, intervention is necessary in patients with symptoms, thrombosis, or risk of rupture such as those harboring aneurysms with a tendency for expansion. The management of SMVA ranges from watchful waiting to surgical intervention; however, a standard treatment approach has not been established. Recently, some cases of portal venous system aneurysm that were successfully treated with interventional radiology, including stent graft placement and coil embolization, have been reported. As illustrated in the present case, interventional radiology should be considered as one of the less invasive therapeutic options for SMVA.