MRI Diffusion Imaging Assesses Inflammatory Bowel Disease Severity

A prospective study published in the Egyptian Journal of Radiology and Nuclear Medicine indicates that diffusion-weighted magnetic resonance enterocolonography (DWI MREC) can serve as a non-invasive tool for assessing the activity of inflammatory bowel diseases (IBD). The research, conducted by a team including Momtaz Thabet Allam Mohammad and colleagues, focused on determining whether apparent diffusion coefficient (ADC) values obtained from MRI scans correlate with histopathological disease activity and endoscopic scores. The study enrolled 50 patients with active IBD, comprising 35 individuals with Crohn’s disease and 15 with ulcerative colitis, aiming to evaluate the diagnostic performance of this imaging technique as a potential alternative to or complement of endoscopic evaluation.

The participants ranged in age from 9 to 72 years, with a median age of 29 years. The cohort included 36 females and 14 males. All patients were diagnosed with active IBD, defined by a Partial Mayo Score of 2 or higher, and were enrolled between December 2021 and March 2024. The study protocol was approved by the Institutional Review Board of the Faculty of Medicine, ensuring ethical compliance for the prospective assessment of imaging biomarkers in this patient population.

Each patient underwent DWI MREC on a 1.5 T MRI scanner, specifically the Siemens Magnetom Sempra, without the use of intravenous contrast agents. The imaging protocol included multiple sequences, such as coronal and axial HASTE, TRUFI, and diffusion-weighted images acquired at b-values of 0, 400, 600, and 800 mm²/s. The quantitative assessment of diffusion was performed at a b-value of 800 mm²/s, a parameter selected based on prior research suggesting optimal diagnostic accuracy for detecting active inflammation in the bowel wall.

Concurrent with the imaging, all patients underwent ileocolonoscopy with biopsies performed within one week of the MRI examination. Ileocolonoscopy was considered the reference standard for detecting disease activity and quantifying severity. Biopsies were assessed by a team of pathologists with 10 to 15 years of experience. In patients with ulcerative colitis, the Mayo Endoscopic Score (MES) was used to assess disease severity, ranging from 0 for normal mucosa to 3 for ulceration and spontaneous bleeding. This dual approach allowed for a direct correlation between radiological findings and histopathological or endoscopic assessments.

The mean ADC values in the diseased bowel segments were measured at 0.98 ± 0.18 × 10⁻³ mm²/s in patients with Crohn’s disease and 0.99 ± 0.11 × 10⁻³ mm²/s in those with ulcerative colitis. Statistical analysis revealed no significant difference in mean ADC values between the two disease groups, with a P-value of 0.805.

However, significant negative correlations were observed between ADC values and the grades of disease activity assessed histopathologically in both groups. In Crohn’s disease, the correlation was significant with a P-value of 0.025, and in ulcerative colitis, the P-value was 0.002. The use of the Kendall rank correlation coefficient confirmed these associations between continuous ADC measurements and ordinal disease activity grades.

Receiver operating characteristic (ROC) curve analysis was employed to evaluate the diagnostic performance of ADC values in distinguishing between mild and moderate-to-severe disease activity. The analysis demonstrated good discrimination, with an area under the curve (AUC) of 0.741 and a P-value of 0.012. An optimal cutoff ADC value greater than 1.04 × 10⁻³ mm²/s yielded a sensitivity of 75.0% and a specificity of 81.6%.

In the subgroup of patients with ulcerative colitis, ADC values showed a significant correlation with the Mayo Endoscopic Score. The Pearson correlation coefficient was -0.539, with a P-value of 0.038. This finding reinforces the utility of DWI MREC in quantifying disease severity in UC, where endoscopic scores are commonly used for clinical management. The correlation implies that lower ADC values are associated with higher endoscopic scores, providing a radiological metric that aligns with established clinical benchmarks.

The study also examined imaging findings related to disease complications. In Crohn’s disease, strictures were the most frequently observed complication. ADC values helped differentiate between chronic fibrotic strictures and active inflammatory strictures. For instance, a patient with a chronic stricture exhibited an ADC value of 1.6 × 10⁻³ mm²/s, indicating no restricted diffusion, whereas patients with active strictures had ADC values ranging from 0.88 to 1.2 × 10⁻³ mm²/s.

Limitations of the study include the relatively small sample size of the ulcerative colitis group, which may affect the generalizability of the results. The study was conducted at a single center, potentially introducing institutional biases in imaging protocols or interpretation. Additionally, endoscopic activity scores were not available for all Crohn’s disease patients, limiting comprehensive comparisons. The cross-sectional nature of the study also prevents the evaluation of temporal changes or treatment responses over time, which would be necessary to fully establish the technique’s role in longitudinal monitoring.

The authors conclude that DWI MREC provides a reliable, non-invasive method for differentiating mild from moderate-to-severe IBD activity. The technique shows potential to complement or replace endoscopy in specific clinical scenarios, such as acute settings or when endoscopy is contraindicated. By offering a quantitative marker of disease activity, DWI MREC could enhance diagnostic workflows and reduce patient burden. The findings support further investigation into the integration of diffusion-weighted MRI into routine clinical practice for the management of inflammatory bowel diseases.

Preparation for the magnetic resonance enterocolonography involved specific protocols to optimize bowel distention and reduce motion artifacts. Patients were instructed to fast for 8 to 10 hours prior to the examination and to receive a laxative to improve bowel cleaning. A rectal enema was performed the day before the MRI to further prepare the colon. On the day of the scan, patients consumed approximately 1500 cc of fluid, consisting of 250 cc of 20% mannitol solution mixed with 1250 cc of water, in divided doses within one hour before the study. For pediatric patients under 12 years of age, the spasmolytic agent dose was adjusted according to body weight at 0.3 mg/kg, and lactulose solution was used in place of mannitol to accommodate their needs. Passive distention of the colon was achieved through the oral solution, a method chosen to enhance patient compliance and minimize loss to follow-up, particularly among female patients who might perceive rectal enemas as embarrassing.

The imaging analysis was performed by two radiologists with more than five and ten years of experience in magnetic resonance enterography, respectively. They independently reviewed the images on separate workstations using the Picture Archiving and Communication System, remaining blinded to the colonoscopy results. Disagreements between the two reviewers were resolved by consensus, and if a consensus could not be reached, a third radiologist with 30 years of experience made the final decision.

Quantitative diffusion assessment involved drawing a round region of interest measuring 10 to 30 mm² on the ADC map, targeting the area of brightest signal intensity on the diffusion-weighted images. This region was typically placed at the thickest point of wall thickening, defined as greater than 3 mm, or at the site of most severe inflammation. The radiologists placed these regions of interest exclusively on the bowel wall, carefully avoiding the lumen, mesentery, or adjacent structures to minimize partial volume effects. Two values were obtained from each region, and their average was estimated to represent the apparent diffusion coefficient for that segment. Additionally, ADC values were estimated for the normal psoas muscle in all patients to provide a baseline comparison for the diseased bowel segments.

Intramural edema was defined as a hyperintense signal on T2-weighted fat-suppressed sequences relative to the normal psoas muscle signal, accompanied by a bowel wall thickness exceeding 3 mm. Ulcerations were identified as small focal losses of signal continuity on the intraluminal surface of the intestinal wall, often containing air or enteric contrast media. Strictures were defined as luminal narrowing in the area of Crohn’s disease with unequivocal upstream dilatation greater than 30 mm.

The statistical analysis utilized IBM SPSS software version 20.0 to process the data. The Shapiro–Wilk test was employed to verify the normality of distribution for quantitative variables. For normally distributed data, the Student t-test was used to compare between two groups, while the Kruskal-Wallis test was applied to abnormally distributed variables to compare more than two groups.

Subject of Research: Evaluation of diffusion-weighted magnetic resonance enterocolonography for assessing inflammatory bowel disease activity.

Article Title: Role of magnetic resonance enterocolonography with diffusion in the assessment of inflammatory bowel diseases activity

Article References: Thabet Allam Mohammad, M., Abdel Aziz Sayed, S., Ahmed Medhat, M., Zidan Mohamed, M., Yahia Hamed, H., & Mohamed Abdel Hakam, A. (2026). Role of magnetic resonance enterocolonography with diffusion in the assessment of inflammatory bowel diseases activity. Egyptian Journal of Radiology and Nuclear Medicine, 57(1), Article 200. https://doi.org/10.1186/s43055-026-01853-6

Image Credits: AI Generated

DOI: 10.1186/s43055-026-01853-6

Keywords: Inflammatory Bowel Disease, Magnetic Resonance Imaging, Diffusion-Weighted Imaging, Crohn's Disease, Ulcerative Colitis, Apparent Diffusion Coefficient, Endoscopy, Histopathology, Medical Imaging, Gastroenterology, Role, magnetic