Portal vein thrombosis in adults: pathophysiology, pathogenesis and management.

Pathophysiology Portal vein obstruction can result from one or several of the following 3 mechanisms: thrombosis, invasion by a malignant tumor (mainly hepatocellular carcinoma) and constriction within a malignant tumor (adenocarcinoma of the pancreas or bile ducts). Compression in the absence of thrombosis, invasion or constriction does not produce portal vein obstruction. Usually, the vein passes round the space-occupying lesions. Clinically, portal vein thrombosis represents an almost pure form of portal vein obstruction. The consequences of portal vein thrombosis are related to the extension of the thrombus. Upstream from the thrombus, there is little effect on the intestine as long as the mesenteric venous arches remain patent. Ischemia results from extension of the thrombus into the mesenteric veins and the mesenteric venous arches (1). It is likely that thrombosis of the arches prevents them from functioning as a collateral circulation to drain intestinal blood toward the adjacent patent territories. Alternatively, reflex arteriolar vasoconstriction might occur when the arches are thrombosed (1). When ischemia is prolonged for several days, intestinal infarction may follow. In 20–50% of the cases, intestinal infarction is responsible for death due to peritonitis and multiple organ failure, even when resection of the infarcted gut is carried out (1–3). Extensive intestinal resection due to venous thrombosis is one of the main causes of the short bowel syndrome. Short bowel stenosis can be a late sequela of mesenteric venous ischemia (4). Downstream from the portal vein thrombus, the consequences for the liver are hardly discernible (5–8). Clinically, signs of liver disease are absent or transient