Small Bowel Disease: Comprehensive Overview and Imaging

The small intestine, also known as the small bowel, plays a crucial role in the digestion and absorption of nutrients. “Small bowel disease” refers to a range of conditions that can affect the small intestine. These include inflammatory diseases (with Crohn’s disease being the most common), celiac disease, infections, issues caused by restricted blood flow (ischemia), benign and malignant tumors, injuries related to medications, and complications such as narrowing (strictures), abnormal connections (fistulas), and pockets of infection (abscesses).

Small bowel disease can manifest in a variety of symptoms, including abdominal pain, diarrhea, bleeding, weight loss, anemia, and malnutrition. Recognizing these symptoms and seeking medical attention can lead to early diagnosis and effective management of the condition. Diagnosing small bowel disease typically involves gathering a detailed medical history, performing laboratory tests, analyzing stool samples, conducting endoscopy or capsule endoscopy procedures, and utilizing cross-sectional imaging.

MRI for small bowel disease

A specialized MRI technique called MR enterography (MRE) is frequently used, as it provides detailed images of the small bowel without exposing patients to ionizing radiation and is recommended by leading medical guidelines for both diagnosis and ongoing monitoring.

Types of Imaging Used for the Small Bowel

  1. MR Enterography (MRE): This imaging technique uses oral contrast to gently expand the small bowel, followed by MRI scans that show the intestinal wall and surrounding tissues. MRE offers excellent soft-tissue contrast and can reveal inflammation, swelling (edema), ulcers, strictures, fistulas, abscesses, and findings outside the intestine—all without the need for radiation exposure.
  2. CT Enterography (CTE): Similar to MRE, CTE uses computed tomography to provide images quickly and is widely available. CT does involve exposure to ionizing radiation or X-rays. The choice between MRE and CTE depends on the clinical scenario, patient-specific factors, and the urgency of the imaging.
  3. Ultrasound: Especially useful in children and at skilled centers, ultrasound can help assess bowel wall thickness and detect increased blood flow. It usually serves as a complementary tool alongside MRE and CTE rather than as a replacement.
  4. Endoscopy/Capsule Endoscopy: Endoscopy allows direct visualization and tissue sampling of the small bowel mucosa. Capsule endoscopy can examine areas not easily reached by standard endoscopy, but cannot assess deeper layers or surrounding tissues. It also carries a risk of capsule retention in cases of narrowing (strictures), making pre-screening with MRE valuable.

How MRI (MR Enterography) Helps Diagnose and Monitor Small Bowel Disease

Detecting and grading inflammation: MRE is especially effective for evaluating Crohn’s disease. It can exhibit signs of active inflammation, including increased bowel wall enhancement, thickening, T2 signal abnormalities (indicating swelling), ulcers, and restricted diffusion. MRE also identifies sinus tracts, fistulas, and abscesses, helping to distinguish between predominantly inflammatory and fibrotic strictures, which is essential for choosing between medical and surgical treatments.

  • Selecting the proper test and reducing radiation exposure: MRE and CTE are supported by evidence-based criteria as primary imaging options in suspected or confirmed Crohn’s disease. For patients requiring frequent follow-ups, especially children, MRE is preferred due to its lack of ionizing radiation and its high diagnostic accuracy.
  • Characterizing strictures: Newly validated MRE definitions and scoring systems enhance consistency in describing fibrostenosing disease, which is crucial for determining the optimal treatment approach, including medical therapy, endoscopic procedures, or surgery.
  • Assessing extra-intestinal disease and complications: MRE not only assesses the bowel wall but also evaluates related findings, such as increased mesenteric blood flow, enlarged lymph nodes, abscesses, and penetrating disease in nearby tissues. These findings can significantly affect treatment decisions and the urgency of treatment.
  • Beyond Crohn’s disease: While Crohn’s disease is the most common inflammatory small bowel condition evaluated with MRE, this technique also helps detect small bowel tumors, identify sources of unexplained gastrointestinal bleeding, and assess complications from celiac disease or prior surgery, often in coordination with gastroenterologists.

What to Expect During MR Enterography at GWIC (Patient Information)

During MR enterography, patients will be guided through a series of steps to ensure a comfortable and successful procedure. This includes administering a measured amount of oral contrast to gently expand the small bowel, the possible use of an antispasmodic medication to reduce bowel motility, and the potential use of an intravenous (IV) contrast agent to enhance visualization of the bowel wall and blood vessels. Patients will be positioned comfortably on the MRI table, with a coil placed over the abdomen and pelvis, and will be asked to perform brief breath-holds while images are acquired.

MR enterography is a safe and comfortable procedure, as it uses a strong magnetic field and radio waves instead of ionizing radiation. Patients should inform staff of any implanted medical devices, prior surgeries, kidney disease, or allergies. Most modern implants are MRI-compatible, and the team will verify this before the exam. Individuals with claustrophobia can discuss comfort strategies in advance, and younger children may require sedation to remain still for high-quality imaging.

When Clinicians Should Consider MRE (Provider Snapshot)

  1. Initial cross-sectional imaging is desirable when small bowel Crohn’s disease is suspected, especially when radiation is to be avoided.
  2. Baseline staging at the time of diagnosis and periodic monitoring of treatment response in patients with known small bowel involvement.
  3. Problem-solving imaging for suspected penetrating disease, abscesses, or for detailed stricture assessment before endoscopic or surgical intervention.
  4. Pediatric cases of inflammatory bowel disease, where minimizing cumulative radiation exposure is prioritized.

Benefits of MR Enterography

  1. It does not use ionizing radiation, making it especially suitable for children and patients who require repeated imaging.
  2. Provides a comprehensive evaluation of the bowel wall and extra-intestinal structures, such as the mesentery, lymph nodes, and abscesses, in a single exam.
  3. Provides actionable details, including distinguishing between inflammation and fibrosis, and identifying penetrating complications, which directly influence treatment choices.

Limitations

  1. Availability and exam length: MRE requires specialized techniques and patient cooperation. In urgent situations, CTE may be preferred because it is quicker and more widely available.
  2. Motion sensitivity: The quality of images depends on how well the bowel is distended and how still the patient remains. Antispasmodic medications and brief breath-holds can help optimize image quality.
  3. Contraindications and precautions: Certain implants or significant kidney problems may restrict the use of MRI or IV contrast agents. Staff will assess device compatibility and individual risk before the exam.

Preparing for Your Exam

Your doctor’s order for MR enterography would include relevant medical history (including prior imaging or endoscopy) and any implanted devices. Patients will be given instructions on how to prepare before arriving for the exam, such as fasting.

Greater Waterbury Imaging Center provides advanced diagnostic MRI services, prioritizing accuracy, comfort, and compassionate care. Our wide-bore scanner and experienced technologists ensure precise imaging results while minimizing patient anxiety and discomfort. Contact us today to learn more about our specialized MRI for small bowel and intestinal disease.