Magnetic Resonance Enterography (MRE) is a specialized medical imaging procedure that uses a magnetic field and radio waves to create detailed pictures of the small intestine. This technique is a modification of a standard magnetic resonance imaging (MRI) scan, specifically tailored to visualize the long, coiled loops of the small bowel. MRE provides physicians with a non-invasive, radiation-free way to look closely at the entire small intestine.
Defining Magnetic Resonance Enterography and Its Indications
MRE uses powerful magnets and radio waves to generate cross-sectional images of the small intestine. Because it does not use ionizing radiation, MRE is often preferred for younger patients or those requiring frequent imaging for chronic conditions. The procedure aims to obtain a clear, detailed view of the small bowel wall and surrounding tissues.
Doctors most often order an MRE to diagnose, monitor, or assess the severity of Inflammatory Bowel Disease (IBD), particularly Crohn’s disease. The high contrast resolution allows the radiologist to detect signs of inflammation, such as thickening of the bowel wall or swelling in the nearby fat tissue. MRE offers an advantage over traditional endoscopy, which cannot reach the entire length of the intestine, and standard CT scans, which use radiation.
MRE is also an effective tool for investigating other small bowel pathologies, including locating sources of gastrointestinal bleeding, identifying tumors, or finding abscesses. The test is highly accurate in depicting complications like strictures (areas of narrowing) and fistulas (abnormal connections between the bowel and another organ or the skin). This ability to see the entire wall and surrounding structures provides comprehensive information that guides treatment planning.
Preparing for the Procedure
Preparation steps are designed to ensure the small intestine is adequately distended for visualization. Patients must fast, typically stopping the consumption of all solid food for four to six hours before the exam. Fasting reduces residue in the small bowel and helps minimize natural bowel movement, which can otherwise blur the images.
The most important preparation step is the administration of a large volume of oral contrast solution, usually consumed at the imaging facility. This solution, often a flavored polyethylene glycol mixture, travels through the gastrointestinal tract, causing the small intestine to fill and distend. Adequate distension is necessary for the radiologist to accurately measure the thickness of the bowel wall and assess for abnormalities.
Patients are typically asked to drink about one to one and a half liters of this liquid over 45 to 60 minutes before the scan begins. This volume can cause a feeling of fullness or a need to use the restroom, which is a normal effect of the contrast material. Before entering the scanner, patients must remove all metallic objects, including jewelry and hairpins, and complete a safety questionnaire regarding implanted medical devices.
The MRE Experience
Once preparation is complete, the examination phase begins with the placement of an intravenous (IV) line. This IV access is used to administer a gadolinium-based contrast agent partway through the scan. This intravenous contrast travels through the bloodstream, enhancing the visibility of blood flow and highlighting areas of active inflammation or tumors within the bowel wall and surrounding structures.
The patient is positioned lying flat on a movable table that slides into the tube-shaped MRI machine. During the scan, the powerful magnets and radio waves create loud thumping and knocking sounds. Earplugs and headphones are provided to protect the patient’s hearing and facilitate communication with the technologist.
A medicine to slow down the natural muscle movements of the bowel, such as glucagon, may also be injected through the IV line to prevent motion blur. The technologist will ask the patient to briefly hold their breath while images are acquired. The total duration of the MRE scan typically ranges from 45 to 60 minutes; remaining still is paramount for obtaining clear, diagnostic-quality images.
Understanding the Results
The images captured during the MRE are interpreted by a radiologist, a doctor specializing in medical imaging. The radiologist examines the small bowel for indicators of disease activity and damage, such as a bowel wall thickness exceeding three millimeters. They look for signs of active inflammation, which may appear as increased brightness (enhancement) of the bowel wall after the intravenous contrast is administered.
The radiologist also searches for strictures, fistulas, and abscesses, which indicate deep, penetrating disease. The characteristics of the enhancement and the presence of edema help differentiate between chronic damage and acute inflammation. These detailed findings are compiled into a comprehensive report and communicated directly to the referring physician. The MRE information is a fundamental element in guiding future medical decisions, such as adjusting medication or planning for surgery.