Ischemic Colitis

Introduction Caused by a reduction in intestinal blood flow from the mesenteric vasculature Arises from occlusion, vasospasm and/or hypoperfusion Consequences can include sepsis, bowel infarction, and death

Introduction, cont. Most frequently affecting the elderly Types: Non-gangrenous: 85%; transient, resolves Severe gangrenous: 15%; life-threatening

Anatomy of the Colon Superior Mesenteric Artery arises from the aorta at L1 or L2 supplies entire small intestine except for the proximal duodenum 4 branches inferior pancreaticoduodenal middle colic right colic ileocolic arteries

Anatomy of the Colon, cont. Inferior Mesenteric Artery arises from the aorta 3 cm proximal to the aortic bifurcation at L3 Branches: left colic artery sigmoid arteries superior rectal artery

Anatomy of the Colon, cont. Ischemic damage to the rectum is rare because it gets collateral flow from IMA and iliac arteries. Colon has collateral circulation, but weak points exist: narrow terminal branches supply the splenic flexure and the rectosigmoid junction these watershed areas are most prone to ischemia during hypotension

Pathophysiology of Colonic Ischemia Non-occlusive ischemia affects the watershed areas of the colon Left colon affected in 75% of patients Only 25% affects the splenic flexure Rectum is less than 5%

Pathophysiology of Colonic Ischemia Aortoiliac surgery post-op rate of colonic ischemia is 1-7% risk factors include older age, renal disease, prior colectomy, longer cross-clamping time risk reduction techniques are not effective

Pathophysiology of Colonic Ischemia Cardiopulmonary bypass rare, but lethal complication high mortality rate increased severity risk factors include long op times, inotropes, intraaortic balloon pumps

Pathophysiology of Colonic Ischemia Myocardial infarction “Ischemic colitis was described in 14 of 100 patients who underwent a colonoscopy within a mean of 15 days after an MI.” Hemodialysis due to atherosclerosis, diabetes, HD-induced hypotension

Pathophysiology of Colonic Ischemia Acquired and hereditary thrombotic conditions unclear if any patients with colonic ischemia should undergo evaluation for hypercoagulability based on limited data younger patients should be worked up

Clinical Manifestations Abdominal pain Mild to moderate rectal bleeding or bloody diarrhea Three progressive clinical stages Hyperactive phase: soon after hypoperfusion or occlusion; severe pain; conservative measures Paralytic phase: pain diminishes, but becomes diffuse Shock phase: electrolyte imbalances occur, dehydration, requires surgery

Diagnosis DDx: infectious colitis, IBD, diverticulitis, carcinoma, Labs: increased lactate, LDH, CPK or amylase may indicate advanced tissue damage Increased WBC may indicate gangrenous necrosis

Diagnosis Plain abdominal x-ray: CT scan: non-specific; only valuable in advanced cases if present, portend a worse prognosis CT scan: typical findings include thickening of the bowel in segmental pattern generally nonspecific and may be normal

Diagnosis Colonoscopy considered if the diagnosis is unclear and no evidence of perforation preferable to contrast enemas overdistention during scope should be avoided

Diagnosis Colonoscopy, cont. Findings: pale mucosa petechial bleeding hemorrhagic nodules cyanotic mucosa “single-stripe sign” rectal sparing

Severe redness, swelling, and almost a bluish appearance is seen in the wall of the bowel. This is a very severe case of ischemic colitis. It may and may not heal and often when it does heal, it heals with scarring.

Diagnosis Barium enema abnormalities are segmental and transient ‘thumbprinting’ is most suggestive and is seen early in the disease; seen in 75% of cases of non-gangrenous ischemia

Barium enema showing stricture formation

Thumbprinting in ischemic colitis

Diagnosis Angiography rarely helpful in most cases, colonic blood flow will have returned already may be indicated if other studies cannot exclude acute proximal mesenteric ischemia not always available; many contraindications

Diagnosis Laparoscopy useful for a “second” look however, pneumoperitoneum greatly effects mesenteric blood flow

Diagnosis MRA pathologic conditions of the mesenteric vessels that can be identified with this technique include: stenosis or occlusion of the proximal mesenteric arteries aneurysms portal hypertension vascular invasion by carcinoma

Treatment Embolectomy, or endarterectomy are only rarely used depends on type and severity of ischemic colitis

Treatment, cont. Non-occlusive ischemia supportive care which includes IVF, bowel rest broad spectrum abx for severe cases NGT if ileus is present vasodilators are not recommended if pt deteriorates, laparotomy and segmental resection are indicated

Treatment, cont. Colonic infarction require surgical intervention bowel preps can precipitate perforation or toxic dilatation despite surgery, mortality following large bowel infarction is as high as 50 to 75 percent

Prognosis Depends on the severity and comorbidities non-occlusive types improve within one or two days gangrenous ischemia is associated with a mortality rate as high as 50 to 70 percent anticoagulation tx is only indicated in pts with mesenteric venous thrombosis or cardiac embolization

Summary Majority of pts develop non-gangrenous ischemia which usually resolves Bloody diarrhea appears within 24 hours of the acute abdominal pain Dx based on H&P, xray, or endoscopy

Summary Angiography or laparoscopy are rarely needed MRA more recently introduced to r/o mesenteric arterial or venous disease Treatment is generally supportive in the absence of colonic gangrene or perforation IVF, Abx, bowel rest Hypercoag w/up for younger pts with recurring ischemia is recommended