MRI enterography is a specialized imaging exam designed to produce detailed pictures of the small intestine. It combines a standard MRI scanner with oral and intravenous contrast agents that make the bowel walls visible in ways a regular MRI cannot. The test is most commonly ordered for people with Crohn’s disease, but it’s also used to evaluate other small bowel conditions including tumors, bleeding sources, and blockages.
Why Doctors Order This Test
The small intestine is roughly 20 feet long and sits deep in the abdomen, making it one of the hardest organs to examine. A standard colonoscopy only reaches the very end of it, and a regular MRI doesn’t show the bowel walls in enough detail to spot inflammation. MRI enterography solves both problems by filling the intestine with a liquid contrast agent, then capturing high-resolution images of the stretched, illuminated bowel wall.
Crohn’s disease is the single most common reason for the exam. Because Crohn’s can affect any part of the digestive tract but favors the small intestine, doctors need a way to see exactly where inflammation is active, how severe it is, and whether complications like narrowing or fistulas have developed. MRI enterography does all of this without radiation, which matters because many Crohn’s patients are young and need repeated imaging over their lifetime.
How to Prepare
You’ll be asked to avoid all solid food for four to six hours before the exam. This fasting period reduces the amount of food residue in the intestine and slows down bowel movement, both of which improve image quality.
When you arrive, you’ll start drinking a large volume of oral contrast, typically around 1,500 mL (roughly a liter and a half) over 45 to 60 minutes. The liquid is usually a solution containing mannitol or a similar osmotic agent. It tastes mildly sweet and slightly thick. The purpose is simple: filling the small intestine with fluid stretches the walls apart so the radiologist can see their full thickness. You’ll drink about 750 mL every 20 to 30 minutes, paced by the technologist.
What Happens During the Scan
Once the oral contrast has had time to reach your small intestine, you’ll lie on the MRI table and slide into the scanner. The machine is loud, and you’ll be given earplugs or headphones. You’ll need to hold still and follow occasional breathing instructions, since even small movements blur the images.
Toward the end of the exam, you’ll receive two injections through an IV line. The first is a small dose of glucagon, a hormone that temporarily stops the bowel from contracting. This brief pause in intestinal movement gives the scanner a still target and dramatically sharpens image quality. The second injection is gadolinium, an MRI contrast agent that flows through your bloodstream and highlights areas of increased blood flow in the bowel wall, a hallmark of active inflammation.
The entire scan typically takes 30 to 45 minutes on the table, though you should plan for about two hours total when you include the drinking period and setup.
What the Images Show
MRI enterography gives radiologists a remarkably detailed view of the bowel wall and the surrounding tissue. Several specific findings help them assess what’s happening inside.
Wall thickening: A healthy small bowel wall is 3 mm thick or less. Anything above that threshold is considered abnormal. Wall thickening is one of the most reliable signs of Crohn’s disease on MRI, with studies showing it correctly identifies the disease 83 to 91% of the time.
Enhancement patterns: After the gadolinium injection, inflamed sections of bowel light up brightly because extra blood is flowing to the area. When inflammation is acute, the wall often shows a layered “target sign,” with a bright inner ring (the inflamed lining), a dark middle ring (swollen tissue), and a bright outer ring (the muscle layer). The intensity of this enhancement correlates with disease activity, giving doctors a way to gauge how aggressive the inflammation is without surgery or endoscopy.
Fat wrapping: In Crohn’s disease specifically, the fatty tissue surrounding an inflamed segment of bowel begins to proliferate and wrap around it. This “creeping fat” pushes neighboring loops of intestine apart and is visible on the scan as increased separation between bowel segments. It’s considered a distinguishing feature of Crohn’s, and its presence on MRI strongly supports the diagnosis.
Beyond these hallmarks, the exam can reveal narrowed segments (strictures), abnormal connections between the bowel and other organs (fistulas), and abscesses in the surrounding tissue.
MRI Enterography vs. CT Enterography
CT enterography uses the same oral contrast approach but captures images with X-rays instead of magnetic fields. Both tests are highly specific, meaning when they identify a problem, they’re almost always right (specificity ranges from 92 to 99% for both). Their sensitivity, the ability to catch every case, is also similar.
The key difference is radiation. A single CT enterography scan delivers a meaningful dose of ionizing radiation, and for conditions like Crohn’s disease, patients may need imaging every year or two for decades. MRI enterography avoids radiation entirely, making it the preferred choice for younger patients, pregnant women, and anyone who needs frequent monitoring. CT enterography is faster and more widely available, so it’s still used when MRI isn’t an option or when speed matters, such as in an emergency.
Side Effects and Safety Considerations
The oral contrast is the most common source of discomfort. The large volume of osmotic liquid pulls water into the intestine, which is the whole point, but it can also cause nausea, cramping, and diarrhea. These effects are usually mild and resolve within a few hours.
Gadolinium, the IV contrast agent, is well tolerated by most people. The primary safety concern involves kidney function. In patients with severely reduced kidney filtration (below 30 mL/min), certain older types of gadolinium carry a risk of a rare but serious condition called nephrogenic systemic fibrosis, which causes thickening and hardening of the skin and connective tissue. Newer formulations of gadolinium have a much better safety profile, and current guidelines consider them safe even for patients with advanced kidney disease. Your care team will check your kidney function beforehand if there’s any concern.
Standard MRI safety rules apply. Metal implants, pacemakers, and certain other devices can be dangerous inside the powerful magnetic field. You’ll fill out a screening questionnaire before the exam, and the technologist will review it with you to confirm it’s safe to proceed. Glucagon, the agent used to pause bowel movement, occasionally causes brief nausea but wears off quickly.
What Happens With Your Results
Radiologists interpreting MRI enterography for Crohn’s disease follow standardized reporting guidelines developed jointly by radiology and gastroenterology societies. This means the report your doctor receives uses consistent terminology to describe findings and their severity, making it easier to compare results over time and coordinate treatment decisions. You’ll typically get results within a few days, and your gastroenterologist will use the findings alongside blood work, symptoms, and endoscopy results to build a complete picture of your disease activity.