Risk factors:The condition is commonly seen in older patients in their sixties to seventies. Most of these patients have previous history of atherosclerotic disease.
- Old age (> 60 years): Hemodialysis, diabetes mellitus, dyslipidemia, hypertension, hypoalbuminemia, constipation-inducing medications, heart failure, peripheral vascular disease, and use of aspirin or digoxin
- Young adults: Constipation, coagulopathy, illicit and prescription drug use, and extreme exertion (endurance athletics)
- Aortic aneurysm repair: Rare complication which compromises colonic blood flow leading to ischemia
Colon vasculature:The vasculature of the colon is thought to play an integral part in the disease.
The superior mesenteric artery (SMA) provides blood flow to the gastrointestinal tract from the duodenum to the mid transverse colon. The inferior mesenteric artery (IMA) supplies blood to the remaining part of the colon and the superior aspect of the rectum. The internal iliac arteries communicate with the IMA via the superior and middle hemorrhoidal arteries.
Collateral flow through the mesenteric branches is provided via the marginal artery of Drummond and the meandering mesenteric artery, also known as the Arc of Riolan. The marginal artery runs parallel to the colon to give branches to the vasa recta.
The marginal artery runs along the splenic flexure, but is absent or underdeveloped in 5% of the population. Injury to the colon is believed to typically occur in the “watershed” areas of the splenic flexure (Grifith point) and sigmoid colon (Sudeck point).
The pathophysiology of ischemic colitis is more often an acute, self-limited decrease in blood supply rather than a specific vascular lesion or embolic event. Angiography, when abnormal, shows narrowing of the small vessels and tortuosity of the long colonic arteries.
Brandt and Boley classification:
- Reversible ischemic colonopathy
- Transient IC
- Chronic ulcerative IC
- Ischemic colonic stricture
- Colonic gangrene
- Fulminant universal
Classic presentation:Classic presentation of ischemic colitis is an elderly patient presenting with bloody bowel movements, abdominal pain, and leukocytosis. The episode is usually preceded by an episode of transient hypoperfusion.
- Acute onset of crampy abdominal pain
- Pass blood mixed with stool within 24 hours
Because patients can present with a wide spectrum of symptoms from vague abdominal discomfort to complete abdominal catastrophe, the diagnosis of ischemic colitis is sometimes challenging to make.
- Early findings: Nonspecific gas pattern or ileus
- Late findings: Thumbprinting sign (submucosal hemorrhage/edema resulting in focal mural thickening)
- Perforation and pneumatosis are consistent with severe injury to the colon.21
Computed tomographic (CT) scan:May appear normal in early or mild cases of ischemic colitis, but may be useful to rule out other causes of abdominal pain or sepsis.
- Non-specific finding: Segmental thickening of the colon wall or pericolic stranding
- Late finding: Pneumatosis or portal venous gas
Colonoscopy with biopsy:In the absence of peritoneal signs, colonoscopy is the diagnostic test of choice to evaluate the degree of ischemia. Colonoscopy remains the most sensitive and specific study available for the diagnosis of ischemic colitis because it allows for detection of mucosal changes by directly visualizing the mucosa.
- Petechial hemorrhages, edematous and fragile mucosa, mucosal bleeding, segmental erythema, scattered erosions, and longitudinal ulcerations
- Severe findings: Loss of haustral markings, cyanosis, and gangrene
- Tissue biopsy: Erosion, granulation tissue hyperplasia, gland atrophy, lamina propria hemorrhage, and macrophages with hemosiderin pigmentation in the submucosaProgressive ischemia: Submucosal edema and hemorrhage seen as bluish–black blebs protruding into bowel lumen (responsible for characteristic thumbprinting sign on radiography)
Medical management:Patients should be aggressively resuscitated and receive broad-spectrum intravenous antibiotics. If the patients are hemodynamically stable and do not have signs of peritonitis, they should undergo urgent colonoscopy. The treatment is dictated by the findings of physical examination and the appearance of the colonic mucosa on endoscopy.
- Bowel rest: Nasogastric tubes used selectively in patients with distention or ileus
- IV fluid resuscitation: Splanchnic focused resuscitation with avoidance of vasoconstrictive medications
- Broad-spectrum antibiotics
Surgical Treatment:In the acute setting, the operative procedure is dictated by the extent of injury to the bowel and the overall condition of the patient. All nonviable bowels must be resected. A damage-control approach may be indicated if intraoperative monitoring reveals hypothermia, coagulopathy, and acidosis. Second look operations may be useful if there are areas of questionable perfusion. The decision to perform an anastomosis should be based on the immediate condition of the patients as well as an assessment of their comorbidities and nutritional status.