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P256. Complete mucosal healing defined by endoscopic Mayo subscore still demonstrates abnormalities by novel iSCAN endoscopic and refined histological gradings

M. Iacucci1, M. Fort Gasia1, J. Love1, G. Kaplan1, R. Panaccione1, S. Ghosh1, X. Gui2,3, 1University of Calgary, Gastroenterology, Calgary, Canada, 2university of Calgary, Pathology, Calagry, Canada, 3The University of Calgary, Gastroenterology, Calgary, Canada

Background

High definition (HD) iSCAN endoscopy can better characterize the mucosa in patients with ulcerative colitis (UC) and may provide more information about inflammation and mucosal healing (MH). However, the gold standard of MH is still histological diagnosis. More sensitive endoscopic and histological assessment is needed in order to better define the MH and to identify subtle remaining histologic abnormalities.

Methods

78 patients (40 male, median age 42 y) with UC were assessed by HD-iSCAN colonoscopy (Pentax EC-3490Fi) as well as by white light endoscopy (WLE). Mayo endoscopic subscore and UC endoscopic index of severity (UCEIS) score were assigned to patients according WLE findings. Mucosal pattern on iSCAN was graded as 1 = normal, 2 = mosaic pattern, 3 = tubular-gyrus, 4 = nodular rosette. The vascular pattern was graded as 1 = normal, 2 = spiral isolated vessels, 3 = crowded tortuous vessels, 4 = irregular vessels. A histological grading and scoring system that assesses all changes possibly seen in IBD was developed for a more comprehensive evaluation. This system (GUI-ECAP system) was designed to reflect all histologic changes in IBD categorized as (1) Extent of inflammation (focal, multifocal, diffuse), (2) Chronicity (crypt architectural alteration, Paneth cell metaplasia), (3) Activity (surface epithelium changes, neutrophilic cryptitis, crypt abscess, crypt destruction, lamina propria mononuclear cellularity, lamina propria neutrophil infiltration, and basal plasmacytosis), and (4) Plus additional findings, including eosinophilia and lymphoid follicles/aggregates. An established histologic grading system, New York Mount Sinai score was used to validate the grading of inflammation.

Results

Of the 78 patients with UC, 23 (29%) had Mayo endoscopic subscore of 0. Of these 23 patients, 18 (78%) had abnormal vascular pattern on iSCAN and 7 (30%) had abnormal mucosal pattern on iSCAN. By using ECAP histologic scoring all 23 patients (100%) showed various histologic abnormalities including crypt architectural alteration [19 (83%)], surface epithelium abnormality [16 (70%)], crypt destruction [3 (13%)], increase in lamina propria mononuclear cells [15 (65%)], basal plasmacytosis [11 (48%)], lamina propria neutrophilic infiltration [5 (21%)] and other additional findings [19 (83%)]. The 23 patients with Mayo endoscopic subscore of 0 had a median UCEIS score of 10 (range 10–14).

Conclusion

The subtle histologic abnormalities underlying the apparently healed mucosa with Mayo endoscopic subscore of 0 can be detected by using refined histological scoring system (ECAP) in combination with iSCAN. iSCAN endoscopy and histologic scoring such as ECAP can detect residual abnormalities in the vast majority of patients with seemingly complete MH in UC.