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mesenteric ischemia (ischemic enteritis)

Etiology: 1) acute ischemia a) obstruction of the superior mesenteric artery - 85% of cases* - due to emboli* in 95% - most emboli orginate in the left atrium - ventricular mural thrombi - atrial fibrillation most likely etiology of emboli b) non-occlusive ischemia due to poor cardiac output - acute heart failure, hypotension, hypovolemia, sepsis [5] - vasopessors, ergot alkaloids, triptans, cocaine, digitalis c) occlusion of the superior mesenteric vein - 10% of cases of bowel ischemia - risk factors - polycythemia vera - liver disease - pancreatic cancer - intra-abdominal abscess or infection - diverticulitis, appendicitis - portal hypertension 2) chronic ischemia (uncommon) a) at least 2 of 3 major splanchnic vessels must be occluded b) risk factors: - hypertension - diabetes mellitus - atherosclerosis* * ref 3 reports 60% of cases are non-thrombotic (low-flow state) * chronic mesenteric ischemia is almost always associated with atherosclerosis [5] Epidemiology: - age of patients with small bowel ischemia varies with cause Clinical manifestations: 1) acute ischemia involving superior mesenteric artery - small intestine ischemia - severe abdominal pain (poorly localized) - pain out of proportion to abdominal exam - peritoneal signs suggest intestinal infarction - urge to defecate - vomiting - diarrhea - bloody diarrhea late feature - short-bowel syndrome - patients appear very ill 2) chronic mesenteric ischemia a) postprandial abdominal pain* - within 60 minutes after eating (typically 30 min) [5] b) sitophobia (fear of eating)* c) weight loss* d) signs & symptoms of atherosclerosis - abdominal bruit e) may progress to persistent abdominal pain even without eating [5] 3) occlusion of the superior mesenteric vein - abdominal pain gradually becoming more severe * classic triad of chronic mesenteric ischemia Laboratory: - complete blood count: - hemoconcentration - leukocytosis - basic metabolic panel: metabolic acidosis - plasma lactate: lactic acidosis (increases anion gap metabolic acidosis) - serum amylase may be elevated - lactate dehydrogenasemay be elevated Special laboratory: - abdominal ultrasound insufficiently sensitive [5] Radiology: 1) CT angiography 1st line imaging study [5] - abdominal CT may show intestinal wall thickening & dilation mesenteric edema, trace free pelvic fluid &/or intestinal pneumatosis (air within the intestinal wall) - images [8] 2) magnetic resonance angiography - lengthy procedure; limited use in acute setting - useful in patients with renal failure [5] 3) splanchnic angiography considered invasive in contrast to CT angiography thus is not first line [5] - procedure does allow for endovascular intervention 4) abdominal radiograph a) ileus b) small bowel obstruction c) later, gas in portal vein Management: 1) acute superior mesenteric artery ischemia: - embolectomy or intra-arterial thrombolysis - broad spectrum empiric antibiotics - surgical resection of necrotic bowel 2) occlusion of the superior mesenteric vein - surgery 3) chronic ischemia: surgical revascularization

Specific

ischemic colitis; ischemic bowel; colonic ischemia

General

visceral arterial disease arterial occlusive disease intestinal ischemia

References

  1. Saunders Manual of Medical Practice, Rakel (ed), WB Saunders, Philadelphia, 1996, pg 338
  2. Mayo Internal Medicine Board Review, 1998-99, Prakash UBS (ed) Lippincott-Raven, Philadelphia, 1998, pg 305-306
  3. Journal Watch 21(13):106, 2001 Endean ED et al Surgical management of thrombotic acute intestinal ischemia. Ann Surg 233:801, 2001 PMID: 11407335
  4. Brandt LJ, Boley SJ. AGA technical review on intestinal ischemia. American Gastrointestinal Association. Gastroenterology. 2000 May;118(5):954-68. PMID: 10784596
  5. Medical Knowledge Self Assessment Program (MKSAP) 14, 15, 16, 17, 18, 19. American College of Physicians, Philadelphia 2006, 2009, 2012, 2015, 2018, 2021.
  6. Pecoraro F1, Rancic Z, Lachat M et al Chronic mesenteric ischemia: critical review and guidelines for management. Ann Vasc Surg. 2013 Jan;27(1):113-22 PMID: 23088809
  7. Wyers MC Acute mesenteric ischemia: diagnostic approach and surgical treatment. Semin Vasc Surg. 2010 Mar;23(1):9-20. PMID: 20298945
  8. Clair DG, Beach JM (images) Mesenteric Ischemia. N Engl J Med 2016; 374:959-968. March 10, 2016 PMID: 26962730 http://www.nejm.org/doi/full/10.1056/NEJMra1503884
  9. NEJM Knowledge+. Nov 22, 2016 http://knowledgeplus.nejm.org/question-of-week/433/
  10. Wang JM, Chang SC. Images in clinical medicine. Acute mesenteric infarction associated with atrial fibrillation. N Engl J Med 2011 Apr 7; 364:1349 PMID: 21470012 Free full text http://www.nejm.org/doi/full/10.1056/NEJMicm1001885
  11. van Dijk LJ, van Noord D, de Vries AC, et al. Clinical management of chronic mesenteric ischemia. United European Gastroenterol J. 2019;7:179-188. PMID: 31080602