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P118 Magnetic resonance enterograghy in operative planning for patients with Crohn’s disease of the small bowel: does timing matter?

A. Patel*1, N. Gouvas1, S. Wadhwani2, R. Lovegrove1

1Worcestershire Acute Hospitals NHS Trust, Department of Colorectal Surgery, Worcester, UK, 2Worcestershire Acute Hospitals NHS Trust, Department of Radiology, Worcester, UK

Background

Cross-sectional imaging is often utilised in the preoperative evaluation of Crohn’s disease to enable planning of surgical approach and to counsel patients effectively regarding the nature of surgery. The aim of this study was to determine the diagnostic accuracy of MRE in patients having imaging within 6 months of surgery compared with those who had it 7–12 months prior to surgery.

Methods

Retrospective review of consecutive patients who underwent surgical resection for Crohn’s disease of the small bowel between March 2015 and August 2018. Data obtained from electronic clinical records. MRE predicted disease location, extent and nature (either stricturing or fistulating) were correlated with operative findings. The sensitivity and positive predictive value (PPV) of MRE across these three domains was calculated for both groups. If the predicted length of disease was within 5 cm of the length described at time of surgery, the MRE length assessment was considered to be accurate. As no patients with negative imaging underwent surgery (true negatives), it is not possible to calculate specificity.

Results

In total, 39 patients were included (M:F 20:19, median age 44 years), of which, 28 had undergone MRE within 6 months prior to surgery (Group 1). There were 7/39 (18%) patients where there was underdistension of the small bowel and 2/39 (5%) where the images were distorted secondary to motion artefact. The table below demonstrates the differences between the two groups across the three domains.

Group 1 (n = 28 patients)Group 2 (n = 11 patients)
Number of males126
Median Age (years)4843
Number of diseased segments4015
Sensitivity (location)89.7%91.7%
Sensitivity (length)47.1%14.3%
Sensitivity (nature)79.5%72.7%
PPV (location)97.2%78.6%
PPV (length)94.1%25.0%
PPV (nature)96.9%66.7%

Comparison of diagnostic accuracy of MRE in Groups 1 and 2.

There were three patients in Group 2 where the MRE suggested a small bowel stricture, however, at time of surgery, there was no evidence of a stricture and a resection was not performed. In comparison, all patients in Group 1 had procedures in keeping with pre-operative planning.

Conclusion

Our study suggests that the sensitivity and PPV of MRE decreases with time. MRI small bowel within 6 months of surgery is advocated to enable accurate pre-operative planning for these patients and to counsel them appropriately about the extent of surgical resection.