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DOP16 The ratio of submucosa thickness to the total bowel wall thickness can be a sonographic parameter to estimate endoscopic remission in Ulcerative Colitis

Miyoshi, J.(1);Ozaki, R.(1);Yonezawa, H.(1);Mori, H.(1);Kawamura, N.(1);Matsuura, M.(1);Hisamatsu, T.(1)

(1)Kyorin University School of Medicine, Department of Gastroenterology and Hepatology, Mitaka-shi, Japan

Background

A less invasive examination that can estimate endoscopic remission is needed. Intestinal ultrasound (IUS) is a promising option. The bowel wall thickness (BWT) is a widely-accepted objective parameter in IUS to assess colonic inflammation, but BWT is influenced by intestinal peristalsis and the volume of luminal content. A feasible, objective index that is not affected by these factors could improve the diagnostic potential of IUS. The submucosa, which is observed as the third layer of the intestinal wall on IUS, becomes swollen and standing out in the active UC. Given BWT and submucosa thickness (SMT) can be influenced by the peristalsis and luminal content simultaneously, we hypothesized that the ratio of SMT to BWT can be an index for submucosal swelling regardless of those factors and this index can be a new parameter to estimate endoscopic remission.

Methods

Inclusion criteria were (1) both IUS and endoscopy (sigmoidoscopy or colonoscopy) for UC were performed in Kyorin University Hospital between April 2019 and December 2020 and (2) time-interval between IUS and endoscopy was within 2 weeks. BWT and SMT were measured based on IUS images for ascending (A/C), transverse (T/C), descending (D/C), and sigmoid colon (S/C), respectively. We defined the submucosa index (SMI) as a percentage of SMT to BWT (Figure 1). When SMT was too thin to be measured, we scored 0 for SMI. The loss of stratification (LOS) was defined as the condition where the submucosa cannot be identified even with BWT > 3 mm (Figure 2). The parts with LOS were considered as inflamed mucosa. Mayo endoscopic subscore (MES) was scored for each part of the colon based on the endoscopic images. MES of 0/1 was defined as the endoscopic remission. Informed consent was obtained in the opt-out method. This study was approved by the Institutional Review Board of Kyorin University School of Medicine (IRB No. 1668).

Results

In total 68 parts of the colon (A/C: 11, T/C: 12, D/C: 14, and S/C: 31) were analyzed. With ROC analysis with the Youden index, the cutoff value of BWT for endoscopic remission was 3.7 mm (AUC: 0.84). Among the parts without LOS, the cutoff value of SMI for endoscopic remission was 47.9 (AUC: 0.75). The positive predictive value for endoscopic remission of the diagnostic criteria (1) BWT ≤ 3.7 mm, (2) BWT ≤ 3.7 mm and no LOS, (3) SMI ≤ 48 (no LOS), and (4) BWT ≤ 3.7 mm, SMI ≤ 48 (no LOS) was 83.3%, 88.2%, 60.7%, and 93.3%, respectively. The negative predictive value was 88.0%, 88.2%, 90.0%, and 86.8%, respectively.

Conclusion

Given the feasibility and objectiveness of assessing bowel wall structure, our findings provide “proof of concept” that SMI can be an additional sonographic parameter for endoscopic remission.

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