Ischemia of the Bowel (Intestinal Ischemia)

How the bowel's blood supply works

Three main arteries from the aorta supply the intestines:

• Celiac artery: stomach, liver, upper duodenum
• Superior mesenteric artery (SMA): small intestine and right colon
• Inferior mesenteric artery (IMA): left colon and rectum

The bowel lining is very sensitive to low oxygen. Within hours of severe ischemia, it starts to die (infarction), allowing bacteria into the bloodstream and risking perforation.

Types of bowel ischemia

Symptoms

Acute mesenteric ischemia

• Sudden, severe abdominal pain, often around the belly button
• Pain that seems much worse than the tenderness found on examination, a classic warning sign
• Nausea, vomiting and an urgent need to empty the bowels
• Later: bloody stools, a swollen and rigid abdomen, fever, confusion and shock as the bowel dies

Ischemic colitis

• Sudden cramping pain, usually on the left side of the abdomen
• An urge to pass stool, followed within 24 hours by bright red or maroon blood mixed with diarrhea
• Usually milder, and most cases improve within days

Chronic mesenteric ischemia ("abdominal angina")

• Dull, cramping pain 15 to 60 minutes after meals, lasting up to a few hours
• Fear of eating ("food fear") leading to significant weight loss
• Bloating, nausea, diarrhea

Risk factors

• Age over 60
• Atrial fibrillation and other heart rhythm problems
• Heart failure and recent heart attack
• Atherosclerosis and peripheral artery disease
• Smoking, high blood pressure, diabetes and high cholesterol
• Hypercoagulable disorders and cancer
• Low blood pressure, dehydration, shock or major surgery (especially aortic surgery)
• Medicines and drugs that constrict blood vessels: cocaine, some migraine drugs, vasopressors, and some constipation and IBS medicines

Diagnosis

1. History and examination: sudden severe pain with a soft abdomen raises suspicion.
2. Blood tests: a raised lactate, high white cell count and metabolic acidosis suggest bowel damage, though early results can be normal.
3. CT angiography: the key test for acute and chronic mesenteric ischemia, showing blocked arteries or veins and bowel wall changes.
4. Colonoscopy: for suspected ischemic colitis, showing patchy inflammation and ulceration, and to exclude other causes.
5. ECG and echocardiogram: to find a heart source of clots.
6. Duplex ultrasound: to screen for narrowing in chronic ischemia.

Treatment

Acute mesenteric ischemia

This is a time-critical emergency:

• IV fluids, oxygen and broad-spectrum antibiotics
• Anticoagulation with heparin to stop clot extension
• Restoring blood flow: surgery to remove the clot or bypass the blockage, or endovascular treatment (clot-dissolving drugs, clot removal, angioplasty or stenting)
• Removing dead bowel (bowel resection), often with a planned "second look" operation 24 to 48 hours later
• Non-occlusive ischemia: treating the underlying low flow state, and sometimes infusing vasodilators directly into the artery

Mesenteric venous thrombosis

Anticoagulation is the main treatment, with surgery if the bowel dies. Long-term blood thinners and investigation for clotting disorders follow.

Ischemic colitis

Most mild cases improve with:

• bowel rest and IV fluids
• treating the cause, such as dehydration or low blood pressure, and stopping triggering medicines
• antibiotics for moderate or severe cases
• surgery if there is perforation, gangrene or failure to improve

Chronic mesenteric ischemia

Angioplasty and stenting, or surgical bypass, restore blood flow and relieve pain, which also prevents progression to acute ischemia. Stopping smoking and controlling vascular risk factors are essential.

Complications and outlook

Acute mesenteric ischemia has a high death rate, often 50% or more, mainly because diagnosis is delayed. Early recognition and treatment greatly improve survival. Survivors who lose large lengths of small bowel may develop short bowel syndrome and need nutritional support. Ischemic colitis usually has a good outlook, with most people recovering fully within 1 to 2 weeks, though a few develop strictures or recurrent episodes.

Frequently asked questions

What are the symptoms of bowel ischemia?

Acute ischemia causes sudden severe abdominal pain, often worse than expected from examination, with nausea, vomiting and sometimes bloody stools. Ischemic colitis causes cramping left-sided pain and bloody diarrhea. Chronic ischemia causes pain after eating and weight loss.

What causes mesenteric ischemia?

Causes include blood clots from the heart (often due to atrial fibrillation), clots forming on narrowed arteries, low blood flow during shock or heart failure, and clots in the intestinal veins. Atherosclerosis, smoking and clotting disorders increase risk.

Is bowel ischemia an emergency?

Acute mesenteric ischemia is a life-threatening emergency that needs immediate treatment to save the bowel. Ischemic colitis is often less severe but still needs prompt medical assessment. Call 911 for sudden severe abdominal pain.

What is the difference between ischemic colitis and mesenteric ischemia?

Ischemic colitis affects the large bowel, is usually caused by temporary low blood flow, and often resolves with supportive care. Acute mesenteric ischemia usually affects the small bowel, is caused by a blocked artery or vein, and needs urgent intervention.

Can bowel ischemia be prevented?

Risk can be reduced by not smoking, controlling blood pressure, cholesterol and diabetes, taking anticoagulants as prescribed for atrial fibrillation, staying hydrated, and treating chronic mesenteric artery narrowing before it causes an acute blockage.