saudigastro.com/patients/ischemic-colitis
Category
Serious
Red flags
5
This article is educational and does not replace your doctor's advice. Seek urgent care for any red-flag symptoms.
What is it?
Like every organ, the colon needs a steady supply of blood carrying oxygen. "Ischemia" means that supply is reduced. When part of the colon is starved of blood, its lining becomes inflamed and may be damaged, causing ischemic colitis. It most often affects older adults and the left side of the colon. In many people the blood flow recovers by itself and the bowel heals within days, but in a minority the damage is severe and needs urgent treatment.
How common is it?
It is the most common form of bowel injury caused by reduced blood flow. It is seen mostly in people over 60, and is more frequent in those with heart or blood vessel disease, though younger people can be affected.
Why does it happen?
Often no single cause is found. The blood supply may drop because of low blood pressure (from dehydration, heart failure or major illness), narrowed or blocked blood vessels, a blood clot, or the colon being squeezed by severe constipation or a blockage. Other contributors include some medicines, major surgery on the aorta or heart, long-distance running or cycling, and certain blood-clotting disorders.
Symptoms
- Sudden cramping belly pain, usually on the left side
- An urgent need to pass stool
- Bright red or maroon blood mixed with stool within about a day of the pain starting
- Diarrhoea
- Nausea or mild vomiting
- Tenderness when the belly is pressed
Red flags — seek urgent medical care
Sudden, severe belly pain, especially pain that seems out of proportion to what the doctor finds on examination
This can signal damage to the small bowel or a severe form of reduced blood flow. Go to the emergency department now.
Fever, a rigid or swollen belly, a fast heartbeat or fainting
May mean a perforation, infection or shock. Call emergency services.
Heavy bleeding or passing large amounts of blood
Needs emergency care and a full assessment.
Repeated vomiting, a swollen belly and not passing wind
May point to a blockage. Seek emergency care.
Atrial fibrillation, heart valve disease or peripheral artery disease together with sudden belly pain
A clot from the heart or an artery problem may be the cause. Seek emergency care without delay.
How is it diagnosed?
Doctors suspect it from your age, risk factors and the typical pain followed by bloody diarrhoea. A CT scan of the abdomen is often done to see the bowel wall and the blood vessels. Blood tests look for infection, dehydration and signs of bowel damage. A colonoscopy, done carefully and usually within a few days, can confirm the diagnosis and exclude other causes such as infection or inflammatory bowel disease. Stool tests may be sent to exclude infection. Your doctor decides the tests.
What the latest science says
Management has moved towards supportive care for mild disease and early identification of those at risk of severe disease. Findings on CT, the pattern of blood tests and the side of the colon involved help predict who may need surgery. Recurrence is uncommon, but looking for and treating underlying vessel or heart problems matters.
Outlook — what to expect
Most people recover fully, often within a week or two, without surgery. Some develop a narrowing of the bowel (stricture) later and need follow-up. Severe cases involving bowel death need urgent surgery and can be life-threatening, which is why prompt medical review is important.
Treatment
Habits & Lifestyle
Do not try to treat sudden belly pain with bloody diarrhoea at home. Get assessed first.
- Seek medical review the same day for sudden belly pain with bloody diarrhoea
- Do not take painkillers such as anti-inflammatory tablets or opioids without medical advice
- Do not use laxatives or anti-diarrhoea medicines until you have been assessed
- Tell your doctor about all your medicines and your heart or vessel conditions
- Do not smoke; it damages blood vessels
Diet
Food advice depends on how unwell you are; in hospital you may be asked to rest the bowel.
- Follow the fasting or fluid instructions of the hospital team
- Once recovering, restart with light, easily digested foods and return to normal gradually
- Drink enough fluids to avoid dehydration, which can lower blood flow to the bowel
- Prevent constipation with fibre and fluids, as advised by your doctor
Medications
Treatment is mostly supportive. Your doctor decides what you need.
- Intravenous fluids to maintain blood flow and hydration
- Antibiotics are sometimes given if there is a risk of infection or moderate to severe disease
- Pain relief chosen by the hospital team
- Medicines that reduce blood flow to the bowel may be stopped; do not stop or change any medicine on your own
- Blood thinners or treatment of heart rhythm problems may be needed if a clot is the cause
Procedures & Surgery
Most people do not need a procedure, but some do.
- Colonoscopy may be performed to confirm the diagnosis
- Surgery to remove the damaged section of bowel is needed if there is perforation, gangrene or a failure to improve
- Procedures to open a blocked artery are used in selected patients with blood vessel disease
- A follow-up colonoscopy may be arranged to check healing and look for narrowing
Living with the condition
- After recovery, attend follow-up to check heart and blood vessel health.
- Return promptly if the symptoms come back.
Questions to ask your doctor
Save this list or print it before your appointment — doctors appreciate prepared patients.
- What caused the reduced blood flow in my case?
- Do I need a colonoscopy or other follow-up tests?
- Should any of my current medicines be changed?
- Could this come back, and what can I do to lower the chance?
- Which symptoms mean I should return to the emergency department?
Was this guide helpful?
Status: Approved for publication by SGA; individual clinician review is ongoing · Published 24/04/2026
For general education only; it does not replace your doctor’s advice. Individual clinician review of this guide is ongoing. SGA clinician? Review this guide