Endoscopic quantification of mucosal surface roughness for grading severity of ulcerative colitis

Background: Mucosal surface roughness is the element of Matts grading system for endoscopic severity of ulcerative colitis. The aims of the present study were to develop an image-processing method for quantifying mucosal surface roughness and to evaluate performance of this method by comparison with visually assessed surface roughness. Methods: A total of 139 digitized colonoscopic pictures from 69 randomly selected patients with ulcerative colitis were used. The red frame of the endoscopic picture was processed for the mean spatial gradient reflecting the surface roughness. Three endoscopists (E1, E2, E3), unaware of the study design were asked to assess the surface roughness by using a visual analog scale (VAS) from 0 to 1. A total of three sessions for surface roughness were performed by each endoscopist on different days. Results: The overall mean gradient was 28.9 +/- 10.9. The mean VAS did not significantly differ among endoscopists (0.42 +/- 0.23 for E1, 0.45 +/- 0.19 for E2 and 0.43 +/- 0.28, P > 0.05). The correlation coefficient of VAS between E1 and E2, between E2 and E3, and between E3 and E1 was 0.957 (P < 0.0001), 0.914 (P < 0.0001) and 0.950 (P < 0.0001), respectively. The mean gradient correlated with the averaged VAS for each endoscopist (r = 0.711 for E1, P < 0.0001; 0.672 for E2, P < 0.0001; 0.826 for E3, P < 0.0001). Conclusion: This method may provide a means for mucosal surface roughness as a pictorial parameter, regardless of the organ studied.