Ischemic Bowel Disease

How the bowel gets its blood supply

Three main arteries from the aorta supply the gut: the celiac artery (stomach, liver, upper duodenum), the superior mesenteric artery (small intestine and right colon) and the inferior mesenteric artery (left colon and rectum). Some areas of the colon, called watershed zones (such as the splenic flexure), lie at the edge of two supplies and are especially vulnerable when blood pressure drops.

Types of ischemic bowel disease

Ischemic colitis

The most common form, mostly in people over 60. A temporary drop in blood flow injures the colon lining. Triggers include dehydration, heart failure, low blood pressure, surgery (especially aortic surgery), constipation, long-distance running, and medicines such as some migraine drugs, decongestants, and constipation drugs that reduce gut blood flow.

Symptoms: sudden crampy pain, usually on the left side, an urgent need to pass stool, then bright red or maroon blood mixed with stool within 24 hours.

Most cases improve within 2 to 3 days and heal within 1 to 2 weeks with supportive care. A minority develop gangrene, perforation or later narrowing.

Acute mesenteric ischemia

This is a life-threatening emergency in which the small bowel can die within hours. Classic features:

• sudden, severe abdominal pain
• pain out of proportion to tenderness on examination
• nausea, vomiting and sometimes a sudden bowel movement
• later: bloody stools, a distended rigid belly, fever and shock

Risk factors include atrial fibrillation, a recent heart attack, heart valve disease, atherosclerosis, clotting disorders, and critical illness.

Chronic mesenteric ischemia

Gradual narrowing of the gut arteries, usually by atherosclerosis, means the bowel cannot get enough extra blood after meals ("intestinal angina"). Symptoms:

• dull or cramping pain 15 to 60 minutes after eating, lasting 1 to 3 hours
• fear of eating (food fear)
• significant unintended weight loss
• sometimes nausea or diarrhea

It is more common in women and smokers and can progress to acute ischemia.

Diagnosis

• CT angiography: the main test for acute and chronic mesenteric ischemia; shows blockages, bowel wall changes and complications.
• Blood tests: lactate may rise in advanced ischemia, but a normal level does not rule it out; white cell count, kidney function.
• Colonoscopy: confirms ischemic colitis and its severity, ideally within 48 hours.
• Duplex ultrasound: for screening chronic mesenteric artery narrowing.
• Heart tests: ECG and echocardiogram to find a source of clots.

Treatment

Ischemic colitis

• bowel rest, intravenous fluids
• treating the cause: improving blood pressure, stopping causative medicines
• antibiotics for moderate to severe cases
• surgery for gangrene, perforation or failure to improve

Acute mesenteric ischemia

• immediate fluids, antibiotics and anticoagulation with heparin
• urgent restoration of blood flow: surgical removal of the clot (embolectomy), bypass, or endovascular treatment (clot-dissolving drugs, stenting)
• removal of dead bowel, often with a planned "second-look" operation
• long-term anticoagulation if the cause is atrial fibrillation

Chronic mesenteric ischemia

• endovascular stenting of narrowed arteries, now the most common treatment
• open surgical bypass in selected cases
• nutritional support
• stop smoking and treat atherosclerosis risk factors with statins and antiplatelet medicines

Mesenteric venous thrombosis

Anticoagulation, with intervention or surgery if bowel is compromised.

Complications

• bowel gangrene and perforation (bowel perforation)
• sepsis and multi-organ failure
• short bowel syndrome after extensive bowel removal
• colonic stricture after ischemic colitis
• malnutrition

Outlook

Ischemic colitis usually has a good outcome, with most mild cases resolving completely. Acute mesenteric ischemia carries high mortality, often over 50%, mainly because diagnosis is delayed; rapid recognition and treatment improve survival. Chronic mesenteric ischemia responds well to stenting, though arteries may narrow again and need repeat procedures.

Frequently asked questions

What are the symptoms of ischemic bowel disease?

Ischemic colitis causes sudden cramping belly pain and bloody diarrhea. Acute mesenteric ischemia causes sudden severe belly pain that seems out of proportion to tenderness, often with vomiting. Chronic mesenteric ischemia causes pain after meals, fear of eating and weight loss.

What causes ischemic bowel disease?

It is caused by reduced blood flow to the intestines. Causes include blood clots from the heart (often with atrial fibrillation), hardened and narrowed arteries, low blood pressure, dehydration, heart failure, clotting disorders and some medicines.

Is ischemic colitis serious?

Usually it is mild and heals within 1 to 2 weeks with fluids, rest and treatment of the cause. Some cases are severe and need surgery. It is important to distinguish it from acute mesenteric ischemia, which is a surgical emergency.

How is mesenteric ischemia diagnosed?

CT angiography is the main test. It shows blocked or narrowed arteries and changes in the bowel wall. Blood tests and, for ischemic colitis, colonoscopy add information. Heart tests may find a source of clots.

Can chronic mesenteric ischemia be treated?

Yes. Narrowed gut arteries can be opened with stents through a catheter or bypassed surgically. This usually relieves pain after meals and allows weight to recover. Stopping smoking and taking statins and antiplatelet medicines help prevent progression.