The treatment of mesenteric venous thrombosis involves anticoagulation alone or in combination with surgery. In patients with acute or subacute mesenteric venous thrombosis, treatment with heparin should be started immediately.
Contrary to previous thinking, surgical exploration is not necessary in all patients with mesenteric venous thrombosis. Patients with peritonitis clearly require emergency surgery. As soon as the diagnosis of mesenteric venous thrombosis is made or confirmed intraoperatively, treatment with anticoagulants should be initiated. Subsequent management is dictated by the surgical findings, which range from a segmental infarction of small bowel to necrosis of the entire bowel, with or without perforation. The aim of resection is to conserve as much bowel as possible. Follow-up (“second-look”) laparotomy, 24 hours later, is often proposed as a way of avoiding the resection of bowel that may be viable.17,18 A second-look procedure is especially useful in patients who have extensive bowel involvement but some venous flow. On rare occasions, thrombectomy can be accomplished successfully when the thrombus is recent and is restricted to the superior mesenteric vein.19 The more diffuse venous thrombosis seen in the acute form of the condition precludes thrombectomy. Arterial spasm is a common finding, and the use of the combination of intraarterial papaverine, anticoagulation, and second-look laparotomy may avert resection of reversibly ischemic bowel.8
Mesenteric venous thrombosis can safely be managed without surgery if there is no evidence of bowel infarction. Unfortunately, there are no precise markers that identify patients who are at risk for bowel infarction. The need for intravenous antibiotics has not been established in the absence of bowel perforation or peritonitis. However, immediate anticoagulation with heparin early in the course of the disease, even intraoperatively, clearly increases survival and significantly decreases the risk of recurrence.5 Systemic heparin therapy is initiated with a bolus injection of 5000 U, followed by a continuous infusion in which the dose is adjusted so that the activated partial-thromboplastin time remains more than twice the normal level. Anticoagulation may be started even in the presence of gastrointestinal bleeding, if the risk of bleeding is outweighed by the benefit of preventing bowel infarction.
Supportive measures include nasogastric suction, fluid resuscitation, and bowel rest (with no food by mouth). Oral anticoagulation with warfarin should be started once there is evidence of the absence of ongoing ischemia. Although varices and consequent bleeding may eventually develop, the benefits of long-term anticoagulation outweigh the risks of bleeding.20 In the absence of an ongoing thrombotic disorder, the duration of anticoagulation may be limited to six months to one year.
We and others have had occasional success using transhepatic portography to instill urokinase or tissue plasminogen activator directly into the thrombus in selected patients.21,22 The use of thrombolytic agents is limited by the risk of hemorrhage and the low rate of success in cases in which the diagnosis has been delayed. Thrombolytic therapy should be considered in patients with thrombosis of large mesenteric veins when the perceived benefit outweighs the risks of the procedure.