Magnetic resonance enterography (MRE) is a type of medical imaging that uses a magnetic field to view details in the small intestine. Doctors can use this technique to diagnose conditions such as Crohn’s disease.
MRE uses the same technology as an MRI scan, but in MRE, people receive a contrast fluid orally and an injection of contrast material into a vein. This fluid then appears on the scan, allowing doctors to see signs of health conditions in the intestines.
This article explores MRE, including what it involves, what it can diagnose, the procedure, and whether it has any risks.
MRE is a technique in medical imaging that uses magnetic fields to obtain highly detailed views of the small intestine.
Before the procedure, a person swallows contrast fluid and receives an injection into a vein. They then lie down in an MRI machine, which creates a magnetic field. The machine detects the contrast fluid, which appears on a monitor for the doctor to examine.
Magnetic resonance enterography (MRE) is a specific technique involving a magnetic resonance imaging (MRI) scanner. The main difference between the two procedures is that a general MRI scan does not necessarily involve using contrast fluids and does not focus specifically on the intestines.
In contrast, the term “enterography” refers to an image or study of the intestine. An MRE only ever investigates this body part.
Other types of medical imaging that focus on the intestines include:
- CT enterography: This is similar to an MRE. An individual swallows a special liquid, and a health worker injects contrast material into a vein. The person then has a CT scan.
- CT enteroclysis: This involves delivering contrast fluid through a tube in the nose or mouth, allowing doctors to see the movement of the fluid in real-time.
- Colonoscopy: This involves inserting a tube with a small camera at the tip into the anus. As a doctor moves the tube up through the intestine, the doctor can see inside it on a connected screen.
MRE can help diagnose diseases of the small intestine, such as:
An MRI can also show signs of bleeding or inflammation and may help doctors monitor the progression of small intestine diseases.
To prepare for an MRE, people must carefully follow their doctor’s instructions. Not following the directions may lead to low quality images and the possibility of having to repeat the procedure.
Instructions for preparing for the MRE may include:
- eating a low residue diet for
3–5 daysbefore the procedure
- fasting for 4–6 hours beforehand
- using a rectal enema
- drinking a large volume of contrast material before the procedure on a timed schedule
Protocols for MRE preparation may vary depending on the imaging center.
An MRE begins with consuming the contrast fluid. A healthcare professional will mix the fluid into water and ask the person to drink it all. There may be a fairly large quantity of this fluid, as its job is to widen the intestines.
After a period of time, the individual will lie on the MRI scanner table, possibly using bolsters or cushions to keep them in position.
The MRI technologist will then move the table backward into the MRI machine and leave the room. The person will be able to talk with the technologist via an intercom.
During the MRI scan, people may hear sequences of beeping, buzzing, or other noises as the technologist runs the machine. Individuals must keep completely still during this process.
For additional contrast fluid, a health professional may insert an IV line into a vein in the arm or hand and inject the fluid through a needle. The technologist will continue taking images.
When the scan is over, the technologist will check the images. If they are clear, they may remove the IV line from the vein and apply a dressing. If the images are not clear, they may ask to take more.
People who have not received sedation before their MRI can go home straight away and resume their usual activities.
MRE and MRI do not have the same risks as X-ray scans, but there are some that people should be aware of.
MRE uses a strong magnetic field, which can pose a
- vagus nerve stimulators
- implantable cardioverter-defibrillators
- insulin pumps
- ear implants
- deep brain stimulators
A person will need to inform their doctor if they have any of these devices. They must also remove any metal jewelry, piercings, and accessories before entering the MRI machine.
MR scanners may be very loud, with some machines reaching up to
Reactions to contrast
Mild symptoms may resolve on their own. If a person develops shortness of breath or difficulty breathing, they need emergency medical attention.
Anaphylaxis: Symptoms and what to do
Anaphylaxis is a severe allergic reaction that can be life threatening. The symptoms develop suddenly and include:
- swelling of the face or mouth
- fast, shallow breathing
- a fast heart rate
- clammy skin
- anxiety or confusion
- blue or white lips
- fainting or loss of consciousness
If someone has these symptoms:
- Check whether they are carrying an epinephrine pen. If they are, follow the instructions on the side of the pen to use it.
- Dial 911 or the number of the nearest emergency department.
- Lay the person down from a standing position. If they have vomited, turn them onto their side.
- Stay with them until the emergency services arrive.
Some people may need more than one epinephrine injection. If the symptoms do not improve in 5–15 minutes, or they come back, use a second pen if the person has one.
Some people may feel claustrophobic inside the MRI machine. Long MRE procedures can make even mild claustrophobia challenging to manage. If an individual knows they feel anxious in small spaces, they can discuss this with their doctor first. There may be ways to ease their anxiety, such as:
- using distractions, such as listening to music or watching a film
- covering the eyes
- relaxation techniques
- having access to a panic button
Unclear risk in pregnancy
Additionally, contrast fluid may enter the fetus’s bloodstream.
Several techniques exist to view the inside of the small intestine. Magnetic resonance enterography, or MRE, is an imaging method that uses a magnetic field from an MRI machine and contrast fluid to view the small intestine. It can provide detailed images to indicate whether a person has bleeding, obstructions, IBD, or other conditions.
MRE procedures require
While MRE does not expose people to X-rays, it does have some risks. People can discuss these with a doctor before the procedure.