The role of Magnetic Resonance Enterography and Small Bowel Ultrasound in Crohn’s Disease

Abstract

Crohn’s disease (CD), a life-long condition resulting in recurrent gastrointestinal inflammation, is estimated to affect one in every 650 people in the UK. Accurate assessment of the disease is crucial to optimise medical and surgical management. Small bowel assessment is heavily reliant on radiological imaging. As the condition predominantly affects young patients, who are more sensitive to the harmful effects of ionizing radiation, ultrasound, and Magnetic Resonance Imaging (MRI) assessment are the preferred radiological investigations. The thesis explores the utility of MR enterography (MRE) and small bowel ultrasound (SBUS) in Crohn’s disease. The thesis is structured as follows: Section A provides an overview on the utility of MRE and SBUS in Crohn’s disease including review and evaluation of the pre-existing literature. It outlines methodological details of the METRIC (MREnterography or ulTRasound in Crohn’s disease) trial: a multicentre, non-randomised, single-arm, prospective comparison study of magnetic resonance enterography and small bowel ultrasound compared to a reference standard in patients aged over 16 years and briefly outlines its main results. Section B details specific substudies of the METRIC trial, investigating the inter-observer variability of the two techniques, influence of oral contrast type and volume on patient experience and quality of luminal distension at MRE and the influence of Diffusion Weighted Imaging and Contrast Enhanced T1 sequences on the diagnostic accuracy of MRE. Section C presents further complementary studies which undertake more in depth analysis of the two imaging techniques: (1) evaluating the relationship between contrast enhanced MRE texture analysis parameters and the presence or absence of histological markers of hypoxia and angiogenesis and (2) evaluating changes in the Dynamic Contrast Enhanced pharmacokinetic and Diffusion Weighted Imaging parameters at MRE relative to clinical response to anti-TNF medication and (3) providing histological validation of SBUS features of inflammation and fibrosis. Section D concludes and summarises the thesis and makes recommendations for future research