From the Guidelines
MR enterography (MRE) is a specialized MRI protocol that evaluates the small bowel using a biphasic oral contrast agent and IV contrast to assess for mural hyperenhancement and active bowel inflammation, as described in the 2022 study by the Journal of the American College of Radiology 1. MRE is a valuable diagnostic tool for detecting Crohn's disease, ulcerative colitis, and other small bowel disorders. The procedure involves ingesting a large volume of oral contrast agent to distend the small bowel, followed by IV contrast administration to enhance image quality. Key features of MRE include:
- Use of biphasic oral contrast agent to distend the small bowel
- IV contrast administration to assess for mural hyperenhancement and active bowel inflammation
- Standard pediatric MRE pulse sequences, including single-shot T2-weighted, balanced steady-state free precession, and diffusion-weighted imaging
- Administration of hypoperistaltic medication to reduce peristaltic motion artifact The role of MRE in clinical practice includes:
- Diagnosis and delineation of disease extent
- Depiction of extra-intestinal manifestations of Crohn's disease
- Detection of penetrating disease complications, such as fistulae and abscesses
- Evaluation of small bowel disease, particularly in cases where optical endoscopy is limited MRE has high diagnostic performance for detecting Crohn's disease-related active bowel inflammation, with sensitivity values ranging from 66% to 95% and specificity values ranging from 64% to 97% 1. Recent evidence suggests that IV contrast may not be necessary for detecting active inflammation in some cases, and diffusion-weighted imaging may provide comparable results without the need for IV contrast administration 1.
From the Research
Definition and Purpose of MR Enterography
- MR enterography (MRE) is a targeted examination of the gastrointestinal tract, particularly the small intestine, without nasojejunal intubation 2.
- It is used to evaluate small bowel disorders, including inflammatory bowel disease, and provides superior soft-tissue contrast, multiplanar capabilities, and lacks ionizing radiation 3, 4, 5.
- MRE is essential for assessing bowel wall changes and extraluminal pathologies/complications, such as those found in chronic inflammatory bowel diseases 6.
Technical Aspects and Indications
- MRE protocols require optimal patient preparation, distension of the bowel using intraluminal contrast agents, and understanding of the technical basis of MRE 6.
- Standard sequences include steady-state free precession sequences, T2-weighted single-shot fast spin echo sequences, and three-dimensional (3D) T1-weighted gradient echo (GRE) sequences with fat saturation after contrast administration 6.
- MRE is indicated for the diagnosis and evaluation of inflammatory bowel diseases, neoplasms, and their assessment during therapy, as well as for detecting intra- and transmural changes, extramural pathologies, and complications 6.
Clinical Applications
- MRE is commonly used to evaluate Crohn's disease and ulcerative colitis, and can help differentiate between these conditions and other small bowel entities that may present with similar imaging features 3, 4.
- It is also used to assess the extent of disease, detect complications, and monitor response to therapy in patients with small bowel Crohn's disease 5.
- MRE can provide valuable information for directing management in patients with small bowel Crohn's disease, and is an essential part of the imaging armamentarium for evaluating small bowel diseases 5, 2.