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:

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