A small bowel MRI scan, also known as magnetic resonance enterography (MRE), is a non-invasive medical imaging procedure designed to visualize the small intestine. This diagnostic tool helps healthcare providers examine the duodenum, jejunum, and ileum, along with surrounding structures, to detect abnormalities. It guides treatment decisions.
How Small Bowel MRI Works
Magnetic Resonance Imaging (MRI) technology creates detailed images of internal organs and tissues using powerful magnets and radio waves. The MRI scanner generates a strong magnetic field that aligns protons within your body’s water molecules. Radio waves then temporarily knock these protons out of alignment. As they realign, they emit signals detected by the machine. Different tissue types produce unique signals, allowing for detailed, three-dimensional images of the small bowel.
To enhance visibility, patients typically drink an oral contrast solution, such as mannitol or polyethylene glycol, before the scan. This liquid distends the small bowel loops, making their walls and internal features clearer. Additionally, an intravenous (IV) contrast agent, often gadolinium, may be injected during the scan to highlight blood vessels and areas of inflammation, further improving image quality. A muscle relaxant, such as Buscopan, might also be administered to reduce bowel movement and minimize image blurring.
Conditions Visualized by Small Bowel MRI
A small bowel MRI identifies and characterizes various medical conditions affecting the small intestine. It is particularly useful for diagnosing and monitoring inflammatory bowel diseases.
Crohn’s disease, an inflammatory bowel disease, is frequently assessed with small bowel MRI. The scan reveals signs of active inflammation, such as bowel wall thickening, increased blood flow, and ulcers. It can also detect complications like strictures (narrowing), fistulas (abnormal connections), and abscesses (pus-filled pockets). MRI is a comprehensive tool for Crohn’s assessment.
Small bowel MRI is also used for suspected celiac disease complications. While celiac disease is primarily diagnosed otherwise, MRI can identify features like changes in the jejunal fold pattern, dilated bowel loops, mesenteric fat inflammation, and lymphadenopathy, indicating complicated forms of the disease. It can also help detect intussusception, where one part of the intestine slides into another.
The scan can identify small bowel tumors, both benign and malignant, which may appear as masses or lesions that narrow the bowel lumen. Additionally, a small bowel MRI can help locate sources of gastrointestinal bleeding that might be difficult to pinpoint with other methods. Other inflammatory conditions, such as enteritis caused by infections, and blockages can also be visualized, allowing for a more accurate diagnosis.
Why Small Bowel MRI is Preferred
Small bowel MRI offers distinct advantages for evaluating the small intestine. A primary benefit is the absence of ionizing radiation exposure, making it suitable for patients requiring repeated imaging, particularly younger individuals with chronic conditions like Crohn’s disease, reducing concerns about cumulative radiation dose.
MRI provides excellent soft tissue contrast, allowing detailed visualization of the bowel wall and surrounding tissues. This helps assess disease activity, identify subtle changes, and detect complications like inflammation, abscesses, or fistulas. It also avoids the need for invasive endoscopic procedures to examine deeper parts of the small bowel.
Preparing for Your Small Bowel MRI
Preparation for a small bowel MRI involves specific guidelines to ensure clear images. Patients are usually asked to fast for about six hours before the scan, though clear fluids like water or black coffee may be permitted. This fasting helps ensure an empty stomach, improving image quality.
A key part of the preparation involves drinking a large volume of oral contrast solution, usually over 45 to 60 minutes, prior to the scan. This liquid helps distend the small bowel, making it easier to visualize. Patients should discuss any medications, allergies, or existing medical conditions, such as kidney disease or diabetes, with their doctor or the MRI staff beforehand.
During the scan, which typically lasts between 30 to 45 minutes, you will lie still on a movable table. The MRI machine can be noisy, so earplugs or headphones are provided. You may be given breathing instructions, such as holding your breath for short periods, to minimize motion artifacts. After the scan, you can generally resume normal activities, though some may experience mild nausea or diarrhea from the oral contrast, which usually resolves quickly.