eMedicine Specialties > General Surgery > Abdomen

Acute Mesenteric Ischemia: Differential Diagnoses & Workup

Author: Chat V Dang, MD, Professor of Emergency Medicine, Charles R Drew University of Medicine and Science; Clinical Professor, Department of Medicine, University of California at Los Angeles
Coauthor(s): Jeff Wade, MD, Staff Physician, Department of Emergency Medicine, Long Beach Community Hospital, Greater El Monte Medical Center; Ashis Mandal, MD, Professor, Department of Surgery, Drew University of Medicine and Science and UCLA College of Medicine
Contributor Information and Disclosures

Updated: Sep 2, 2008

Differential Diagnoses

Other Problems to Be Considered

Ovarian torsion
Small bowel obstruction
Volvulus of midgut
Splenic vein thrombosis

Workup

Laboratory Studies

• In general, laboratory studies are not helpful in diagnosing AMI. No serum marker is sensitive or specific enough to establish or exclude the diagnosis of AMI. Waiting for laboratory results should not delay radiographic studies if serious suspicion of AMI exists.
• CBC may be within the reference range initially, but the WBC count eventually rises as the disease progresses. Leukocytosis and/or leftward shift are observed in over 50% of cases. The hematocrit is elevated initially from hemoconcentration due to third spacing, but it decreases with GI bleeding.
• Amylase levels are moderately elevated in over 50% of patients, but this finding is nonspecific.
• Phosphate levels were initially thought to be sensitive, but later studies showed a sensitivity of only 25-33%.
• ABG: Metabolic acidosis is observed late in disease course, but this is a nonspecific finding.
• Lactate is elevated late in the clinical course. Levels that are persistently within the reference range strongly indicate a diagnosis other than AMI (sensitivity 96%, specificity 60%).
• D-dimer has been suggested to possibly be helpful based on one small clinical study reported in 2001 and on one experimental study in rats.⁶ Clinical experience is lacking to validate the role of D-dimer in the screening and diagnosis of AMI.

Imaging Studies

• Plain abdominal films  
  • Findings on plain films of the abdomen often are normal in the presence of AMI. However, plain films are warranted to exclude identifiable causes of abdominal pain, such as perforated viscus with free intraperitoneal air.
  • Positive findings are usually late and nonspecific and include ileus, small bowel obstruction, edematous/thickened bowel walls, and paucity of gas in the intestines. More specific signs, such as pneumatosis intestinalis, that is, submucosal gas (see Media file 1); thumbprinting of the bowel wall; and portal vein gas, are late findings. In one study of 23 cases of bowel infarction, 30% of the patients demonstrated focally edematous bowel wall (thumbprinting) and/or pneumatosis intestinalis.
• Computed tomography scan
  • CT scan helps exclude other causes of abdominal pain.
  • CT angiography has a sensitivity of 71-96% and a specificity of 92-94% for AMI. In clinical practice, CT angiography is ordered much more frequently than classic angiography. CT angiography is noninvasive, readily available, and the preferred modality for MVT (90% sensitivity).
  • CT scan may show pneumatosis intestinalis, portal vein gas, bowel wall and/or mesenteric edema, abnormal gas patterns, thumbprinting, streaking of mesentery, and solid organ infarction. Bowel wall edema is the most common finding on CT scan. It represents submucosal infiltration of fluid or hemorrhage into ischemic bowel. Arterial occlusion may show nonenhancement of the vessels. MVT usually shows a thrombus in the SMV or portal vein.
  • Serial CT angiograms can be used to monitor patients treated nonsurgically with anticoagulation.
• Angiography
  • Angiography has been the criterion standard to aid in diagnosis and presurgical planning. It also plays an important role in pharmacologic infusion therapy. However, angiography is less and less resorted to in clinical practice. Sensitivity is reported to be 88% for AMI.
  • An embolus appears as a sharp cutoff of flow near the origin of the middle colic artery. Thrombus appears as a more tapered occlusion near the origin of the SMA. NOMI is characterized by narrowing of the origins of multiple SMA branches, alternating dilation and narrowing of the intestinal branches (ie, "string of sausages" sign), spasm of the mesenteric arcades, and impaired filling of the intramural vessels.
  • Angiography is actually a second-line study in patients with a strong suspicion of MVT because false-negative findings are common. Findings with MVT include thrombus in the SMV, reflux of contrast into the aorta, prolonged arterial phase with accumulation of contrast and thickened bowel walls, extravasation of contrast into bowel lumen, and filling defect in the portal vein or complete lack of venous phase.
• Ultrasonography
  • Duplex sonography studies are highly specific (92-100%) but not as sensitive (70-89%) compared to angiography. The examination cannot detect clots beyond the proximal main vessels nor can it be used to diagnose NOMI. Ultrasound is considered a second-line study for AMI. It is often less useful in the presence of dilated fluid-filled loops of bowel.
  • Some studies show usefulness similar to CT scanning if duplex scanning is performed for MVT. It may show a thrombus or absent flow in the involved arteries or veins. Other possible findings include portal vein gas, biliary disease, free peritoneal fluid, thickened bowel wall, and intramural gas.
• Magnetic resonance imaging/magnetic resonance angiography
  • MRI and MRA provide findings similar to CT scan in AMI. Sensitivity of MRA is 100% and specificity is 91%. MRA is particularly effective for evaluating MVT.
  • The main drawbacks are the expense and the time required. In the future, rapid MRA may supplant angiography.
• Echocardiography findings may confirm the source of embolization or show valvular pathology.

Other Tests

• Intraoperative fluorescein administration: During laparotomy, 1 g of fluorescein is infused. Viable bowel fluoresces brightly under a Wood lamp. This allows the surgeon to better evaluate the segments that need resection. It may be performed at the primary operation or during a 24-hour second-look operation.
• ECG may show myocardial infarction or atrial fibrillation.

Procedures

• Nasogastric tube decompression helps relieve distension and allows evaluation for upper GI bleeding.
• Diagnostic peritoneal lavage may recover the serosanguineous fluid associated with bowel infarction; this is not a preferred study if AMI is suspected.
• Foley catheterization allows for monitoring of urinary output as an indicator for minimal fluid resuscitation.
• In patients with intestinal angina, percutaneous transluminal angioplasty and stenting of the celiac and/or mesenteric arteries have been reported with variable short- and long-term patency rates. A multi-institutional, randomized, controlled clinical trial is needed to define the optimal conditions for their application.

• Search for CME/CE on This Topic »

• Mesenteric Ischemia (Emergency Medicine)
• Abdominal Angina (General Surgery)
• Mesenteric Artery Ischemia (General Surgery)

• Environmental Exposures and Injuries Center
• The Bends Overview
• The Bends Causes
• The Bends Symptoms
• The Bends Treatment