The Diagnostic Role of Magnetic Resonance Enterography in Crohn's Disease

An Updated Review of Techniques, Interpretation, and Application

Hina Arif-Tiwari, MD; Bobby Kalb, MD; Surya Chundru, MD; James Costello, MD; Cary G. Sauer, MD, MSc; Diego R. Martin, MD, PhD, FRCPC; Fayez Ghishan; Steve Goldschmid, MD

Disclosures

Appl Radiol. 2013;42(12):5-15. 

In This Article

Abstract and Introduction

Abstract

Crohn's Disease (CD) is a chronic illness characterized by transmural involvement of the bowel wall and mainly affects young adults. Currently, computed tomography enterography (CTE) and magnetic resonance enterography (MRE) are the only 2 imaging modalities that can visualize submucosal tissues throughout the small bowel. Although CT is highly utilized for evaluating CD, in the authors' experience, CT does not match MRE for producing the soft-tissue contrast useful to reliably differentiate between inflammation and chronic fibrotic changes. The authors note that MRE more accurately monitors the effects of medical therapy and triaging patients for surgical intervention.

Introduction

Crohn's disease (CD), a chronic illness characterized by transmural involvement of the bowel wall, mainly affects young adults with a relapsing and remitting course. Clinical presentation typically involves nonspecific symptoms that can be associated with an array of acute active and chronic disease, as well as related to complications from primary bowel pathology that includes the extra-enteric tissues within the abdomen or pelvis. An optimal imaging technique can noninvasively assess the bowel wall for changes in active or chronic CD, can identify complications related to transmural CD, and can be used to monitor the disease safely with minimal or no X-ray exposure.

Crohn's disease involves the small bowel in 80% of cases and can be challenging to diagnose and monitor. In addition, CD involves the full thickness of bowel wall; submucosal inflammation is responsible for tissue destruction and penetration, leading to such complications as fibrosis, strictures, and fistulae. These processes are responsible for the most serious morbidities whereas, in contrast, disease restricted to mucosa is not associated with such sequelae.

While endoscopy with biopsy is generally considered the diagnostic reference standard, this combination evaluates only the mucosa; it does not assess inflammation or fibrosis within the submucosa or deeper tissues. Therefore, these optical techniques alone may under-represent the extent of disease, particularly when considering that the mucosa has a high capacity for repair.

The overarching objective of imaging is to diagnose CD, to assess the location, mural and extramural extent and severity of disease, and to assess for complications such as stricture, bowel tethering, obstruction, or abscess. Cross-sectional imaging, unlike optical techniques, can evaluate submucosal and deeper tissues and extraintestinal complications of CD. Currently, computed tomography enterography (CTE) and magnetic resonance enterography (MRE) are the only 2 imaging modalities that can visualize submucosal tissues throughout the small bowel. CT generally is highly utilized,[1] but there is growing concern over ionizing radiation and cancer risk. In contrast to CTE, MRE does not expose patients to ionizing radiation, and it can differentiate between inflammation and fibrosis as the cause of submucosal inflammation (Table 1). These advantages may be used to monitor the effects of medical therapy more accurately, to detect residual active disease even in patients showing apparent clinical resolution,[2] and to triage patients for surgical intervention more accurately.

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