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P143 The Usefulness of Ultra-low Dose CT colonography for Assessing Mucosal Inflammation in Patients with Ulcerative Colitis

M. Miyamura*1, K. Takeuchi1, T. Arai1, R. Kasai2, A. Yamada1, Y. Suzuki1

1Toho University, Sakura Medical Centre, Division of Gastroenterology, Department of Internal Medicine, Sakura, Japan, 2Toho University, Sakura Medical Centre, Radiology, Sakura city, Japan

Background

Mucosal healing (MH) at endoscopy is a major therapeutic goal in ulcerative colitis (UC). Endoscopy, however, is invasive, time consuming and uncomfortable. Computed tomography colonography (CTC) has emerged as a noninvasive screening procedure for colorectal neoplasia but radiation exposure is a major concern if applied to patients with UC. We aimed to examine ultra-low dose CTC (uCTC) for evaluating mucosal inflammation in patients with UC.

Methods

Patients with UC underwent colonoscopy and uCTC acquired with low dose at 75 mAs or ultra-low dose at 5 mAs levels on the same day. As bowel preparation, patients took low residue diets on the previoursday and 1.8L of isotonic magnesium solution on the day. CTC images were evaluated for UC, in which selected valuables (loss of colonic haustra, luminal narrowing, bowel wall thickness, mural hyper-enhancement and mesenteric hyper-vascularity in both air images or multiplanar reconstruction (MPR) images) were scored from 0 to 1 in the worst affected segment of colon, to create a novel uCTC score from 0 to 5. Endoscopic severity was evaluated by Mayo Clinic endoscopy sub-score (eMCS, 0-3) and the two score were correlated.

Results

In 90 patients the median uCTC score was 3.56 (range 0-5) and eMCS 1.89 (range 0-3). The uCTC score correlated with eMCS (r = 0.727, p< 0.001). The CTC score for each Mayo e-score were as follows (mean±SD): score 0, 0.77 ± 0.77; 1, 2.56 ± 1.40; 2, 3.69 ± 1.69; 3, 4.83 ± 0.34. The uCTC score showed significant differences between endoscopic activity and MH (eMCS 0 vs 1 P<0.001; 1 vs 2 or 3, P<0.01 and <0.001, respectively). Furthermore, uCTC air images alone revealed a significant relationship with eMCS, even with ultra-low dose CTC at 5 mAs levels.

Conclusion

uCTC may be a non-invasive tool to assess mucosal activity in UC and may be a technique to determine MH. Ultra-low dose CTC resolves concern about radiation exposure.