MRI small bowel (MR enterography): preparation, what happens and results

The small bowel is the part of the digestive tract that digests food and absorbs nutrients after the stomach, and it has three parts: the duodenum, jejunum and ileum. The Norfolk and Norwich University Hospitals leaflet explains that the scan looks at all three and takes detailed pictures for the doctor.

MRI scanners use a powerful magnet and radio waves with a computer to produce images of internal structures. The Royal United Hospitals Bath leaflet says that for MR small bowel, fluid is drunk before the scan to distend the small bowel so that it can be well seen on the MRI images. This is why the test is also called MR enterography.

Wrightington, Wigan and Leigh Teaching Hospitals says small bowel imaging helps to evaluate, or rule out, conditions such as Crohn’s disease and inflammatory bowel disease. The Norfolk and Norwich leaflet says the scan helps the doctor understand why you have been feeling unwell, and shows whether there is any active inflammation (sore areas) or narrowing within the small bowel.

The NHS says there is no single test to diagnose Crohn’s disease and that hospital tests may include endoscopy, colonoscopy, biopsy and scans such as MRI, CT or ultrasound. The Royal United Hospitals leaflet notes that MRI does not use ionising radiation, unlike X-ray based tests.

Instructions differ between hospitals and your own appointment letter takes priority. The leaflets give the following general picture.

You will be asked to drink a special solution, with Wrightington, Wigan and Leigh naming preparations such as Klean-Prep, Moviprep, lactulose or mannitol, over up to an hour. Norfolk and Norwich says it is important to drink the full amount, and that juice can be added to flavour it. Some patients experience a laxative effect, so the toilets are shown to you first. If you have a stoma, the leaflet advises bringing extra bags because they fill quickly.

A cannula is then placed in a vein. Wrightington, Wigan and Leigh explains that you receive two injections: the first is a muscle relaxant (Buscopan) used to settle bowel movement that could blur the images, and the second is an MRI contrast dye (gadolinium) that helps to highlight the blood supply to the organs.

During the scan you lie on the scanner bed and stay very still. Wrightington notes that most patients are asked to lie on their front, which reduces movement from breathing, and that you may be asked to hold your breath for a few seconds. The scanner is noisy, so you are given headphones or earplugs, and you are given a buzzer to speak to the radiographer.

Norfolk and Norwich says you may have cramping, wind-like pain for the first 24 hours, caused by the drink, and that paracetamol is usually all that is needed. Blurred vision or a dry mouth should last no longer than 20 minutes and are caused by the contrast fluid, and you are not discharged until it is safe for you to leave. Wrightington says temporary effects of Buscopan can include blurred vision, a dry mouth or a faster heart rate.

In rare cases, Buscopan can worsen previously undiagnosed glaucoma and cause symptoms such as red or itchy eyes. Wrightington advises seeking urgent medical attention if this happens within 48 hours after your scan. You may be asked to stay in the department for up to 30 minutes after the injection as a precaution, and it states that serious side effects are very rare.

Wrightington says the scanner is open at both ends and brightly lit, and that about 1% of patients may feel claustrophobic. The radiographers are used to putting people at ease. The NHS general MRI page advises talking to a healthcare professional beforehand if you are anxious or have a fear of small spaces, and says you may be able to have a medicine to help you relax or bring someone to support you.

Because this scan takes longer than many MRIs and includes a drink that works on the bowel, it is worth telling the department in advance about stomas, bowel urgency and anything that would make lying still for a period hard.

A radiologist studies the images and writes a report to the consultant who referred you. Wrightington says this report is sent to the referring consultant. The NHS says in general that MRI results usually take 1 to 2 weeks and that you may need a follow-up appointment; ask the referring team how you will be told.

A normal scan does not always rule out disease and an abnormal one is read alongside blood tests, stool tests and endoscopy. The NHS notes it often takes time to get a diagnosis of Crohn’s disease because the symptoms vary and can be similar to other conditions.

The NHS says to ask for an urgent GP appointment or get help from NHS 111 if you have black or dark red poo or bloody diarrhoea. Seek urgent medical advice through NHS 111 if you develop severe tummy pain, persistent vomiting or a high temperature, particularly if you have known Crohn’s disease, and call 999 if you feel seriously unwell.