Evaluating luminal and post-operative Crohn’s disease activity on magnetic resonance enterography: A review of radiological disease activity scores

Abstract

Magnetic resonance enterography (MRE) is a non-invasive, radiation-free imaging modality that facilitates the assessment of transmural Crohn’s disease activity. It offers advantages over ileo-colonoscopy, which is limited to mucosal-level evaluation, cannot routinely assess small bowel segments proximal to the terminal ileum, and is unable to detect extra-luminal complications. Despite these advantages, the lack of standardised criteria for defining and appraising radiologic disease activity on MRE has contributed to variability in interpretation and clinical application. In response, multiple MRE-based scoring systems have been developed to quantify radiological Crohn’s disease activity in both luminal and post-operative settings. Radiological disease activity scores specific to luminal Crohn’s disease include the magnetic resonance index of activity (MaRIA), simplified MaRIA, Nancy score, London score, Crohn’s disease magnetic resonance imaging (MRI) index, Clermont score, paediatric inflammatory Crohn’s MRE index, MRE global score, MRE index, and modified Clermont score. The MR score and the MRI in Crohn’s disease to predict postoperative recurrence index have been specifically developed to evaluate post-operative disease recurrence in Crohn’s disease. Nevertheless, heterogeneity in scoring parameters, variability in computational complexity, and a lack of consensus regarding optimal score selection, have impeded widespread clinical adoption of radiological disease activity scores. This narrative review aims to summarise the key imaging features of luminal Crohn’s disease, explore their integration into existing MRE scoring indices, and critically compare the structure, strengths, and clinical applicability of each. Furthermore, MRI scores specific to post-operative Crohn’s disease evaluation, and the assessment of cumulative bowel wall damage using the Lemann index will also be discussed.

Keywords: Crohn’s disease; Imaging; Radiological disease activity; Magnetic resonance imaging; Magnetic resonance enterography; Transumural healing

Core Tip: Magnetic resonance enterography (MRE) offers a non-invasive, radiation-free method of evaluating transmural disease activity and extra-enteric complications of Crohn’s disease. As the role of imaging grows in monitoring Crohn’s disease activity and therapy response, standardised and validated scoring systems are essential. Several MRE-based indices have been developed to quantify radiological Crohn’s disease activity reliably. These tools aim to mirror the role of endoscopic scores by providing reproducible and clinically relevant assessments of Crohn’s disease activity. Integrating these scores into clinical practice and future research promises to enhance objective disease evaluation and support more tailored, evidence-based management of Crohn’s disease.