Chronic Mesenteric (Small Bowel) Ischemia

Etiology and PathogenesisTop

Chronic mesenteric ischemia refers to impaired perfusion of the small intestines resulting from chronic occlusion of the mesenteric arteries.

Causes: The majority of cases are due to atherosclerosis of the aorta, superior mesenteric artery, celiac artery, or less commonly inferior mesenteric artery (35%-50% of cases). Patients typically present with symptoms when they have high-grade occlusion or stenosis of ≥2 mesenteric vessels. Less common causes include Dunbar syndrome (compression of the celiac artery by the median arcuate ligament [also referred to as median arcuate ligament syndrome]), fibromuscular dysplasia of arteries, aneurysm or dissection of the aorta(with possibly inadvertent coverage of mesenteric vessel origin by grafts from subsequent operative management of these conditions), or thromboangiitis obliterans (Buerger disease).

Clinical Features and Natural HistoryTop

In patients with atherosclerosis, collateral vessels form over time due to the gradual narrowing of the vessels. Therefore, perfusion to the bowel can be maintained without bowel compromise. Depending on the time course of the disease and whether there is a superimposed acute event affecting systemic perfusion, patients can present with mild symptoms or with acute mesenteric ischemia.

1. Symptoms: The characteristic symptoms include:

1) Intestinal angina: Crampy epigastric abdominal pain starting a few minutes after a meal and lasting 1 to 3 hours; the pain is most severe after heavy and fatty meals.

2) Fear of food.

3) Cachexia (weight loss in 80% of patients) due to the fear of pain with eating.

4) Persistent diarrhea.

Less typical symptoms include nausea, vomiting, and early satiety (in 30% of patients; usually in patients with occlusion of the celiac artery). A high index of clinical suspicion is required due to the nonspecific symptoms.

Physical examination is nonspecific. An abdominal bruit may be audible.

2. Risk factors: The disease typically develops in tobacco smokers with clinically manifested atherosclerosis of other vascular beds, especially of the lower extremities, coronary arteries, or renal artery.

3. Natural history: Ischemia is typically transient, but acute-on-chronic mesenteric ischemia can occur with thrombus formation. Intestinal necrosis occurs in ~15% of patients.

DiagnosisTop

Chronic mesenteric ischemia presents a diagnostic challenge.

Diagnostic Tests

1. Laboratory tests: There are no diagnostic laboratory investigations.

2. Imaging studies: Although dual-modality ultrasonography (with color Doppler) is a reasonable diagnostic study for high-grade stenotic lesions, computed tomography angiography (CTA) of the abdomen and pelvis is the first-line initial test to identify atherosclerosis and exclude other diseases. CTA and magnetic resonance angiography (MRA) have high sensitivity and specificity (>90%). Arteriography is used for diagnostic confirmation if noninvasive testing is nondiagnostic or during endovascular procedures.

3. Endoscopic evaluation: Upper and lower endoscopy should be considered to exclude alternative diagnoses (eg, celiac disease, peptic ulcer disease, gastrointestinal malignancies).

TreatmentTop

1. Conservative management: Nutritional assessment and support are important. Smoking cessation and pharmacologic preventive measures to limit atherosclerosis should be considered (eg, antiplatelet therapy; blood pressure, dyslipidemia, and blood glucose optimization). Anticoagulation is considered if there is associated thrombus.

2. Revascularization: Consider revascularization (percutaneous endovascular angioplasty or stenting versus open surgical endarterectomy or bypass grafts) in symptomatic patients with documented severe stenosis. Endovascular procedures are being performed more frequently and offer lower rates of postprocedural morbidity compared with open procedures; however, it is unclear whether they are truly superior to open procedures, as they potentially have higher rates of long-term recurrence of the disease.Evidence 1Weak recommendation (benefits likely outweigh downsides, but the balance is close or uncertain; an alternative course of action may be better for some patients). Low Quality of Evidence (low confidence that we know true effects of the intervention). Quality of Evidence lowered due to the observational nature of the included studies. Terlouw LG, Moelker A, Abrahamsen J, et al. European guidelines on chronic mesenteric ischaemia - joint United European Gastroenterology, European Association for Gastroenterology, Endoscopy and Nutrition, European Society of Gastrointestinal and Abdominal Radiology, Netherlands Association of Hepatogastroenterologists, Hellenic Society of Gastroenterology, Cardiovascular and Interventional Radiological Society of Europe, and Dutch Mesenteric Ischemia Study group clinical guidelines on the diagnosis and treatment of patients with chronic mesenteric ischaemia. United European Gastroenterol J. 2020 May;8(4):371-395. doi: 10.1177/2050640620916681. Epub 2020 Apr 16. PMID: 32297566; PMCID: PMC7226699. Cai W, Li X, Shu C, et al. Comparison of clinical outcomes of endovascular versus open revascularization for chronic mesenteric ischemia: a meta-analysis. Ann Vasc Surg. 2015 Jul;29(5):934-40. doi: 10.1016/j.avsg.2015.01.010. Epub 2015 Mar 7. Review. PMID: 25757988. Revascularization may also be considered in asymptomatic patients undergoing surgical procedures on the aorta or renal arteries for other reasons; although the role of prophylactic treatment is limited.