Mesenteric venous thrombosis is seen predominantly in middle-aged patients presenting with vague symptoms, which makes this a challenging diagnosis to make in the acute care setting. Risk factors for MVT include recent injury (causing trauma to the vasculature), recent surgery (causing stagnant blood flow), inflammatory conditions, and hypercoagulable states.1 In this patient’s case, no risk factors were identified; although the majority of cases of MVT will have an identifiable risk factor.2 Still, 21% to 49% of cases of MVT are considered idiopathic.1,3It is possible that our patient had a prior undiagnosed pancreatitis associated with his history of alcoholism that contributed to his thrombosis. Pancreatitis and other inflammatory conditions, including diverticulitis or inflammatory bowel disease, are more commonly associated with thrombus formation in the large veins, as opposed to an undiagnosed hypercoagulable state, which would more likely affect distal venuoles, vasa recta, or venous arcades.1,5 The patient’s mild transaminitis was likely secondary to hepatic congestion from the venous thrombus extending to the splenic-portal vein confluence and intrahepatic portal vein. One study looked at patients with pancreatitis and found that 16.7% of their study population had an SMV thrombus, while 4.1% had a SMV thrombus with a concomitant portal vein thrombus.6
Although there are no pathognomonic laboratory findings of MVT, elevated lactate, leukocytosis, and elevated D-dimer levels may be helpful in supporting the diagnosis.7,8 A recent study found that elevated D-dimer levels may be a specific marker in the early recognition of acute SMV thrombosis, as well as predicting risk, outcomes, and treatment options.8 However, emergency physicians should maintain a high index of suspicion in patients with concerning features of the disease, since normal laboratory values, including lactate, do not reliably exclude the diagnosis.
Computed tomography scanning and CT angiography (CTA) are quite helpful in diagnosing MVT. Ultrasound of the upper abdomen may also play a role, noting dilated or thickened bowel wall with intraluminal air or echogenic material in the superior mesenteric vein or portal vein.9 Although magnetic resonance venography most reliably demonstrates thrombi, its lack of widespread availability makes CT with IV contrast the preferred initial study.3Computed tomography not only has high sensitivity, but also offers alternative diagnoses in the undifferentiated presentation.1One study found CT to be 100% sensitive in detecting any abnormality associated with MVT or bowel ischemia.10 Common CT findings of MVT include dilated and thickened bowel loops, mesenteric fat standing, ascites, a halo or target appearance of bowel, vessel filling defects from a thrombus, and pneumatosis intestinalis.11 The latter usually indicates transmural infarction, and can extend as portomesenteric vein gas.11 Of note, if the initial CT scan is non-diagnostic and a high clinical suspicion for mesenteric ischemia remains with no alternative diagnosis, CTA is the gold standard.3,7Expeditious diagnosis of MVT is imperative, given the potential complications of intestinal infarction, submucosal hemorrhage secondary to edema, and third spacing of the venous outflow into the bowel wall due to collateral vessels being unable to redirect blood flow in conjunction with complete venous occlusion.12Not all MVTs progress to infarction, given the extensive collateral circulation. Early diagnosis, however, is crucial for conservative management to be effective.9Acute MVT without signs of infarction necessitates anticoagulation therapy to decrease clot propagation and recurrence.1 In addition, prophylactic antibiotics to limit bacterial translocation, and bowel rest are advised.13,14 If the patient is unresponsive to anticoagulation, thrombolytic and endovascular therapies may be of benefit in select patients.15 Once intestinal ischemia or infarction develops, the prognosis is poor: mortality approaches 75% with infarction.1 If signs of bowel infarction are present, a laparotomy must be performed promptly, although in most cases, delayed patient presentation makes small bowel resection unavoidable.9 Further testing for hypercoagulability is recommended, particularly in isolated thrombosis, since long-term anticoagulation therapy may be necessary if a coagulopathy is discovered.1
Mesenteric venous thrombosis is atypical in a young, healthy patient. However, due to high mortality rates with disease progression, it is important to consider in any patient with unrelenting abdominal pain and vague gastrointestinal symptoms of uncertain cause, even in those without risk factors. Early detection and management of MVT before progression to mesenteric ischemia and infarction considerably lowers the mortality rate. Emergency physicians must be vigilant when treating a patient with abdominal pain out of proportion to physical examination, unrelenting pain despite analgesic medications, or repeat ED visits for the same abdominal complaints.