Diagnostic Approach for Ischemic Bowel Disease

Clinical Presentation

The American College of Radiology recommends CT angiography (CTA) of the abdomen and pelvis as the first-line diagnostic test for suspected ischemic bowel disease, with a sensitivity and specificity of 95-100% for detecting vascular abnormalities, in patients presenting with abdominal pain out of proportion to physical examination findings, which should be assumed to be mesenteric ischemia until proven otherwise 1, 2
Acute mesenteric ischemia typically presents with abdominal pain out of proportion to physical examination findings, which should be assumed to be mesenteric ischemia until proven otherwise, and the clinical scenario helps differentiate between mesenteric arterial emboli, mesenteric arterial thrombosis, non-occlusive mesenteric ischemia (NOMI), or mesenteric venous thrombosis 3
Chronic mesenteric ischemia often presents with post-prandial abdominal pain, weight loss, and fear of eating, with a more indolent clinical presentation, and peritonism signs (rebound tenderness, guarding) are associated with ischemia and/or perforation 4, 5
Abnormal vital signs including tachycardia, tachypnea, cool extremities, mottled skin, slow capillary refill, and oliguria should alert clinicians to critical conditions, with low serum bicarbonate levels, low arterial blood pH, high lactic acid level, and marked leukocytosis may suggest intestinal ischemia 5

The World Journal of Emergency Surgery states that there are no laboratory studies that are sufficiently accurate to definitively identify ischemic or necrotic bowel, however, certain markers may assist in diagnosis, such as low serum bicarbonate levels, low arterial blood pH, high lactic acid level, and marked leukocytosis, which may suggest intestinal ischemia 3, 5
Elevated D-dimer may assist in diagnosis but lacks specificity, and hyperamylasemia may be present in intestinal ischemia, according to the World Journal of Emergency Surgery 3, 5

The American College of Radiology recommends CTA of the abdomen and pelvis as the first-line imaging test for suspected mesenteric ischemia, which can detect vascular abnormalities (arterial and venous occlusions), signs of bowel ischemia, including abnormal wall enhancement, bowel wall thickening, mesenteric edema, pneumatosis, and portal venous gas 1, 6
A triple-phase study (non-contrast, arterial, and portal venous phases) is important for identifying the underlying cause and evaluating for bowel complications, according to the Journal of the American College of Radiology 4
MR angiography (MRA) can be considered as an alternative for patients with renal insufficiency or severe reactions to iodinated contrast, but has limitations in evaluating for ischemic bowel changes compared to CT, as stated by the Journal of the American College of Radiology 4

The Journal of the American College of Cardiology recommends that for suspected acute mesenteric ischemia, CTA abdomen/pelvis (triple phase) should be performed immediately, and if CTA is contraindicated, consider MRA, and if initial testing is negative but clinical suspicion remains high, consider conventional angiography 8
For suspected chronic mesenteric ischemia, CTA or duplex ultrasound should be performed as initial screening, and if CTA is contraindicated, MRA or duplex ultrasound is recommended, according to the Journal of the American College of Cardiology and Circulation 7, 8

The World Journal of Emergency Surgery states that once diagnosed, immediate fluid resuscitation should commence to enhance visceral perfusion, broad-spectrum antibiotics should be administered immediately, and unless contraindicated, patients should be anticoagulated with intravenous unfractionated heparin, and prompt laparotomy should be performed for patients with overt peritonitis 3