Extrahepatic portal vein aneurysm in which the acute thrombogenic process triggered by trauma confirmed by abdominal ultrasonography: a case report.

Extrahepatic portal vein aneurysm (PVA) is a rare condition in which the extrahepatic portal vein is partially dilated into a sac-like or spindle-like shape. Usually, patients are followed, but surgery is considered in cases of rupture, thrombus, or enlargement. We report a case of thrombus formation in an extrahepatic portal vein aneurysm following trauma that resulted in regression of the aneurysm and extrahepatic portal vein occlusion. Immediately after the trauma, ultrasonography showed moderately hyperechoic structures and comet signs along the vessel wall of the aneurysm and turbulent blood flow in the aneurysm, like in a whirlpool. There were floating point-like echogenic features, which were presumed to be microthrombi. In other words, the trauma might have triggered Virchow's triad: changes in the vessel wall, changes in blood properties, and blood stagnation. This is a valuable case in which ultrasonography imaging revealed interesting changes during the thrombus formation process inside an extrahepatic portal vein aneurysm. The aneurysm's size was reduced by thrombus-induced organization, but the main trunk of the portal vein became deficient in blood flow, resulting in extrahepatic portal vein occlusion. This case is suggestive of the mechanism of extrahepatic portal vein occlusion.