Abnormalities of the distal terminal ileum in people with cystic fibrosis assessed using magnetic resonance imaging

Background The terminal ileum (TI) is commonly affected in people with cystic fibrosis (pwCF), but limited quantitative information is available on its appearance and dimensions. This study aimed to use magnetic resonance imaging (MRI) to: 1) measure the diameter of the distal TI in healthy volunteers (HVs) and pwCF; 2) test the hypothesis that the diameter of the TI in pwCF is larger than in HVs. Methods Twenty-six adult pwCF (23 on modulators) and 30 HVs participated. A commercial image analysis platform (Entrolytics, Motilent, UK) was used to measure the long and short axes diameters of the TI on cross-sectional images, along the most distal 5 cm before the ileo-caecal valve. The cross-sectional area of the TI was calculated assuming an elliptical shape. Results (mean±SD) pwCF had a larger TI compared with HVs: the long axis TI diameter (1.6 ± 0.3 cm for HVs versus 2.7 ± 0.7 cm for pwCF, p < 0.0001), the short axis TI diameter (1.2 ± 0.3 cm versus 2.2 ± 0.6 cm respectively, p < 0.0001) and the TI cross-sectional area (1.6 ± 0.7cm² versus 4.9 ± 2.5cm² respectively, p < 0.0001). Sixty-five% of pwCF showed heterogeneous, faeces-like chyme presence in the TI. Conclusions This study showed that the TI is enlarged and filled with heterogeneous, faeces-like chyme in pwCF compared with HVs. These findings are in keeping with earlier surgical reports. Increased chyme viscosity and/or impaired motility may lead to accumulation of chyme in the TI in pwCF. New treatments correcting these abnormalities such as secretagogues could be evaluated using the new MRI-derived TI diameter and area endpoints.