Mesenteric venous thrombosis can be acute, subacute, or chronic.8 Acute mesenteric venous thrombosis is diagnosed in patients whose symptoms begin suddenly, the subacute form in those who have abdominal pain for days or weeks without bowel infarction, and the chronic form in those who present with complications of portal-vein or splenic-vein thrombosis such as esophageal variceal hemorrhage.

Acute thrombosis is associated with a definite risk of bowel infarction and peritonitis. In patients with subacute mesenteric venous thrombosis, abdominal pain is prominent, but neither bowel infarction nor variceal hemorrhage is likely. Patients with chronic mesenteric venous thrombosis do not have pain and have extensive venous collateral circulation. Management is therefore geared toward preventing variceal hemorrhage. In rare instances, patients with a long history of abdominal pain may have an intestinal infarction, thus blurring the distinction between acute and subacute presentation. Accordingly, the following discussion focuses on acute and subacute mesenteric venous thrombosis together; the chronic form will be addressed separately.

The hallmark of mesenteric ischemia, whether it is due to arterial or to venous thrombosis, is abdominal pain that is not explained by the physical findings (Table 2). The abdominal pain of acute or subacute mesenteric venous thrombosis is midabdominal and colicky, suggesting an origin in the small bowel. Although the duration of symptoms varies, 75 percent of patients have had symptoms for more than 48 hours before they seek care.9 Nausea, anorexia, vomiting, and diarrhea are also common. Hematemesis, hematochezia, or melena occurs in about 15 percent of patients,8 but occult blood will be detectable in the stool in nearly 50 percent of patients.7 The nonspecific nature of the abdominal symptoms and the rarity of the condition often delay the diagnosis. About half the patients have a personal or family history of deep venous thrombosis or pulmonary embolism.4,9 The initial physical findings may be entirely normal. Fever, guarding, and rebound tenderness develop later and indicate progression to bowel infarction; peritonitis develops in one third to two thirds of patients with acute mesenteric venous thrombosis. Hemodynamic instability can result from the collection of fluid within the bowel lumen or the abdominal cavity, and systolic pressures of less than 90 mm Hg denote a poor prognosis.8

Table 2. Comparison of Acute Mesenteric Venous Thrombosis and Acute Mesenteric Arterial Thromboembolism.

Patients who present with postprandial symptoms may be mistakenly thought to have a peptic ulcer, and those with diarrhea may be assumed to have an intestinal infection or Crohn’s disease. When severe abdominal pain is the sole symptom, pancreatitis is often suspected. The onset of ascites in a patient with a history or family history of thrombotic disease should heighten the clinical suspicion of mesenteric venous thrombosis.