Mesenteric venous thrombosis.

A 32-year-old man with ulcerative colitis requiring total colectomy and ileostomy developed intermittent, severe abdominal pain and fevers 2 days postoperatively. His examination was remarkable for a temperature of 97.2°F, heart rate of 76 bpm, and blood pressure of 134/80 mm Hg. His abdominal examination was notable for diffuse, moderate tenderness on palpation without rebound or guarding. He underwent computed tomographic (CT) scan of the abdomen and pelvis, which demonstrated thrombosis of the superior mesenteric vein (Figure 1). A vascular medicine specialist was consulted. Overview Mesenteric venous thrombosis (MVT) describes acute, subacute, or chronic thrombosis of the superior or inferior mesenteric vein or branches. MVT may present with acute abdominal pain or may be an asymptomatic incidental finding on abdominal imaging. MVT accounts for 1 in 5000 to 15 000 inpa-tient admissions and 1 in 1000 emergency surgical laparotomies for acute abdomen. 1 The incidence of MVT has increased over the past 40 years, likely as a result of the greater use of abdominal CT. 2 Age at presentation varies, depending on the underlying pathogenesis of MVT, although it is most common in the fifth and sixth decades of life. There is a slight male predominance. 1 The true incidence of chronic MVT is likely to be underestimated because it is often asymptomatic. Two large series demonstrated that chronic MVT accounts for 24% to 40% of total cases of MVT. MVT often results from a combination of hypercoagulability, endothelial injury, and stasis, any of which may be part of a local or systemic process (Table). In patients with inherited hypercoagulability, MVT can occur spontaneously as an idiopathic event or after brief or relatively minor insults. In others, it can develop as a result of inflammation caused by inflammatory bowel disease, intra-abdominal infection , or abdominal trauma. Abdominal surgery, which can result in both endo-thelial injury and inflammation, also precipitates MVT. Malignancy is present in 4% to 16% of acute MVT cases. 1 Up to 37% of MVT cases appear to be idiopathic. Pathophysiology Inflammation and other local factors often contribute to thrombus formation in large mesenteric veins, whereas systemic hypercoagulability is more likely to be responsible for thrombus formation in smaller vessels. 1 Normal mesenteric venous drainage mirrors the mesenteric arterial circulation. At rest, the bowel can tolerate marked reductions in blood flow because only 20% of capillaries are needed to provide adequate oxygen delivery to tissues. 4 Even in …