Definition, Etiology, PathogenesisTop
Colonic ischemia is caused by insufficient perfusion of the intestinal wall that leads to hypoxia, reperfusion injury, and colonic inflammation. Ischemic colitis is the most frequent and less severe form of colonic ischemia. Segments of the intestines that are particularly vulnerable to ischemia include the region of the splenic flexure, descending colon, and rectosigmoid.
In most cases, ischemic colitis results from a low-flow state with no single identifiable cause. It can also result from occlusion of arteries (atherosclerosis, embolism, or thrombosis) and/or rarely of mesenteric veins.
Clinical Features and Natural HistoryTop
Colonic ischemia occurs more frequently in women and older patients.
1. Symptoms: The classic symptoms of ischemic colitis are mild to moderate crampy left lower abdominal pain, urgent need to defecate, and bloody diarrhea within 24 hours of onset. Physical examination is nonspecific.
2. Risk factors include:
1) Medical conditions: Cardiovascular disease (eg, atherosclerosis, peripheral vascular disease, congestive heart failure, atrial fibrillation, hypertension), diabetes mellitus, chronic obstructive pulmonary disease, rheumatoid arthritis.
2) Procedures: Abdominal aortic aneurysm repair, cardiopulmonary bypass, aortoiliac instrumentation.
3) Drugs: Constipation-inducing drugs, immunomodulators (eg, anti–tumor necrosis factor alpha), drugs of abuse (eg, cocaine).
4) Rare risk factors include long-distance running, sickle cell crisis, and hypercoagulable states.
3. Natural history: Most cases are self-limited. Symptoms usually resolve within a few days and colon healing occurs after a few weeks even when untreated. However, irreversible ischemia can occur in some cases. Necrosis and perforation of the colon wall with diffuse peritonitis and hemodynamic instability may develop rapidly. Long-term complications such as strictures can occur.
4. Mortality: Mortality rates range from 4% to 12%. Increased mortality rates occur in patients with chronic kidney disease or chronic obstructive pulmonary disease, in those requiring surgical management, and in patients with isolated right colon ischemia.
1. Laboratory tests:
1) Serology: There are no specific markers for ischemic colitis. Results are helpful in predicting disease severity. Decreased hemoglobin and albumin levels and the presence of metabolic acidosis predict a more severe disease. In addition, investigations that may suggest advanced tissue damage include increased lactate, lactate dehydrogenase, creatine phosphokinase, and amylase.
2) Stool tests: Clostridium difficile toxin assay, culture, and ova and parasite tests should be performed to exclude infectious colitis.
2. Imaging: Abdominal plain films are usually nonspecific and therefore not very helpful, apart from the cases where they demonstrate signs of advanced ischemia (eg, thumbprinting) or perforation. Nonspecific findings include ileus or colon distension. Computed tomography (CT) with IV and oral contrast has replaced barium enema and is the current standard of care. Signs suggestive of ischemic colitis are nonspecific, such as bowel-wall thickening and fat stranding; the results may also be completely normal. Computed tomography angiography (CTA) or traditional angiography is only performed when acute mesenteric ischemia is suspected.
3. Colonoscopy: The diagnosis is confirmed with early colonoscopy (or flexible sigmoidoscopy) with biopsies within 48 hours. Contraindications to colonoscopy are peritonitis or signs of irreversible ischemic damage. Endoscopic findings include erythema, edema, hemorrhagic lesions, and/or ulcerations. Pathognomonic features are mucosal infarction and ghost cells. These lesions are frequently segmental with sharp transition between the normal and the affected mucosa. The rectum is relatively unaffected due to its dual blood supply from mesenteric and iliac arteries (as opposed to ulcerative colitis, which involves the rectum).
1. Conservative management: Most cases improve with bowel rest, fluid resuscitation, removal of precipitating factors, and nasogastric tube decompression if ileus is present.
2. Antibiotic therapy: Broad-spectrum empiric antibiotics in moderate to severe disease are recommended.Evidence 1Strong recommendation (benefits clearly outweigh downsides; right action for all or almost all patients). Low Quality of Evidence (low confidence that we know true effects of the intervention). Quality of Evidence lowered due to the evidence being based on animal studies and no human studies looking directly at the effect of antibiotics. Yoshiya K, Lapchak PH, Thai TH, et al. Depletion of gut commensal bacteria attenuates intestinal ischemia/reperfusion injury. Am J Physiol Gastrointest Liver Physiol. 2011 Dec;301(6):G1020-30. doi: 10.1152/ajpgi.00239.2011. Epub 2011 Sep 8. PubMed PMID: 21903760.
3. Anticoagulation: Anticoagulation is only indicated if ischemic colitis is due to mesenteric venous thrombosis or cardiac embolization.
4. Surgical treatment: Resection of the affected segments of the intestines with or without an end stoma is reserved for the most severe cases. Indications for surgery include perforation; clinical, radiologic, or endoscopic features suggestive of gangrene (eg, peritonitis); failure of medical treatment; or rarely massive bleeding in the setting of ischemic colitis. Uncommonly, patients who remain symptomatic or have recurrent episodes for a few weeks after presentation may require surgery. In patients with intestinal strictures resection of the affected segments of the colon is indicated if the patients are symptomatic or there is diagnostic uncertainty (ie, suspicion for cancer).