Patient Education3 min read

CT & MR Enterography

Overview

The small bowel is a long coiled tube that ordinary scopes cannot easily reach. Enterography is a scan designed to show it clearly. Before the scan you drink a large amount of a special liquid (a neutral oral contrast) over about an hour, which fills and gently stretches the small bowel so its walls can be seen. A contrast dye is usually given through a vein as well. CT enterography uses X-rays, with a short scan time, and gives fine detail of the wall and the tissues around it. MR enterography uses a magnet and radio waves with no radiation, and shows the bowel wall, inflammation and complications well. A medicine may be given to relax the bowel so the pictures are sharper.

Who needs it

People with suspected Crohn’s disease, to confirm the diagnosis and see how much of the bowel is involved

People with known Crohn’s disease, to check for strictures, fistulas or abscesses, or how well treatment is working

People with unexplained small bowel bleeding, anaemia, pain or weight loss after other tests

People with suspected small bowel tumours, or an abnormal capsule camera result

Risks

•

Fullness, bloating, nausea, vomiting or diarrhoea from the large drink (common, short-lived)

•

CT: exposure to radiation, which is kept as low as reasonably possible but adds up with repeated scans, which is a reason to prefer MR in young people and for frequent follow-up

•

Allergic reaction to contrast dye, rarely severe; the dye can affect people with reduced kidney function, so kidney tests may be checked first

•

MRI: unsafe with some implants or metal; anxiety in the enclosed scanner and noise; the muscle relaxant can raise heart rate or affect eyes in some people (not suitable for some with glaucoma or heart conditions)

•

Scans may not catch every small area of disease, and findings must be interpreted with your symptoms, blood tests and scope results. Sometimes further tests are needed.

•

Seek urgent help after the scan if you develop a rash that spreads, swelling of the face or lips, difficulty breathing, chest tightness or severe belly pain.

Before the procedure

You will usually be asked to fast for several hours before the scan. The centre will give exact times and may ask for a light diet the day before.

You will need to drink a large volume of the contrast liquid over about an hour at the centre; it can taste unpleasant and may cause fullness, bloating, nausea or loose stool.

Tell the team if you have kidney disease, diabetes (especially if you take metformin), allergy to contrast dye or iodine, asthma, or if you are pregnant or may be pregnant. CT uses radiation and is usually avoided in pregnancy.

For MRI, also tell the team about pacemakers, defibrillators, cochlear implants, brain aneurysm clips, metal in the eye and other implants, and about any fear of small spaces. Remove metal items. Bring device cards.

Tell the team about your medicines. Do not stop any unless told to. Your team will advise on diabetes medicines on the day. Arrange to be accompanied if you are given a sedative. If you fast for Ramadan, ask for a suitable time slot.

When to See a Doctor

Call your doctor or go to emergency if after the procedure you have severe or worsening abdominal pain, fever, repeated vomiting, heavy bleeding, black stools or fainting.

Why it is done

These scans show the small bowel wall and the tissues outside it, which a colonoscopy cannot see. They are used to diagnose Crohn’s disease, measure how widespread and active it is, find narrowing (strictures), fistulas (abnormal channels) and abscesses (pockets of infection), check the response to treatment, and look for tumours or other causes of unexplained bleeding, pain or weight loss. MR enterography is often chosen for young people and for repeated scans because it avoids radiation, while CT is faster and is often preferred in urgent situations or when MRI is not suitable.

During the procedure

At the centre you drink the contrast liquid in portions over roughly 45 to 60 minutes. A small drip is placed in your arm. For MRI you may be given a muscle-relaxing medicine by injection to stop the bowel moving, which can briefly blur vision or cause a dry mouth, and a contrast dye. You lie on a table that moves through a scanner: CT is a short ring-shaped scanner and the scan itself takes only seconds to a couple of minutes, while MRI is a longer tube-shaped scanner that is noisy and takes about 20 to 45 minutes. You must lie still and hold your breath for short periods. Contrast dye through the drip can give a warm feeling, a metallic taste or a sensation as if you passed urine; these pass quickly.

After the procedure

You can usually go home straight away, eat, and return to normal activities. The contrast liquid can cause loose stools or diarrhoea for a few hours. Drink plenty of fluids to help clear the dye. If you were given a muscle relaxant, wait until your vision is normal before driving. If you had a sedative, do not drive that day. A radiologist reviews the images and reports to your doctor.

When you get the results

A radiologist reports the scan, usually within a few days, sooner if urgent. Your doctor will go through the results with you, explain what they mean for your diagnosis and treatment, and decide on the next steps.

Alternatives

Alternatives include small bowel ultrasound (no radiation, available in some centres), capsule endoscopy (swallowing a tiny camera, which shows the lining but not the outside, and needs caution if a narrowing is suspected because the capsule can get stuck), balloon-assisted enteroscopy (a deep scope that allows biopsies and treatment), and stool tests such as calprotectin for inflammation. Each has strengths and limits. If you decline, the extent or complications of the disease may be missed.

Questions to ask your doctor

• Should I have a CT or an MR enterography, and why?

• Are the contrast dye and the muscle relaxant safe for my kidneys, heart and eyes?

• How should I manage my diabetes medicines on the day?

• How can I make the large drink easier to finish?

• How often will I need repeat scans, and what is the radiation exposure over time?

Source and review

This guide comes from the Saudi Gastroenterology Association (SGA) patient library, prepared by the Approved for publication by SGA; individual clinician review is ongoing. Last reviewed: 2026-04-24. It is for education and does not replace your doctor's advice.

Frequently Asked Questions

What is CT & MR Enterography?

Why is CT & MR Enterography done?

What are the risks of CT & MR Enterography?

Fullness, bloating, nausea, vomiting or diarrhoea from the large drink (common, short-lived); CT: exposure to radiation, which is kept as low as reasonably possible but adds up with repeated scans, which is a reason to prefer MR in young people and for frequent follow-up; Allergic reaction to contrast dye, rarely severe; the dye can affect people with reduced kidney function, so kidney tests may be checked first; MRI: unsafe with some implants or metal; anxiety in the enclosed scanner and noise; the muscle relaxant can raise heart rate or affect eyes in some people (not suitable for some with glaucoma or heart conditions); Scans may not catch every small area of disease, and findings must be interpreted with your symptoms, blood tests and scope results. Sometimes further tests are needed; Seek urgent help after the scan if you develop a rash that spreads, swelling of the face or lips, difficulty breathing, chest tightness or severe belly pain.

How do I prepare for CT & MR Enterography?

You will usually be asked to fast for several hours before the scan. The centre will give exact times and may ask for a light diet the day before; You will need to drink a large volume of the contrast liquid over about an hour at the centre; it can taste unpleasant and may cause fullness, bloating, nausea or loose stool; Tell the team if you have kidney disease, diabetes (especially if you take metformin), allergy to contrast dye or iodine, asthma, or if you are pregnant or may be pregnant. CT uses radiation and is usually avoided in pregnancy; For MRI, also tell the team about pacemakers, defibrillators, cochlear implants, brain aneurysm clips, metal in the eye and other implants, and about any fear of small spaces. Remove metal items. Bring device cards; Tell the team about your medicines. Do not stop any unless told to. Your team will advise on diabetes medicines on the day. Arrange to be accompanied if you are given a sedative. If you fast for Ramadan, ask for a suitable time slot.