Linear-array EUS improves the accuracy of predicting deep submucosal invasion in non-pedunculated rectal polyps compared with radial EUS: a prospective observational study.

BACKGROUND: Radial endoscopic ultrasound (EUS) is typically used to estimate the depth of rectal polyp invasion, however, there are no data on linear EUS in this setting and its relative accuracy compared to radial EUS. METHODS: In this prospective cohort study, 89 patients with non-pedunculated rectal polyp who underwent linear EUS or radial EUS were prospectively enrolled. The invasion depth was measured for each polyp and categorized as mucosal to shallow submucosal(SMs) or deep submucosal(SMd) invasion. Invasion measurements were compared with the final diagnosis on histopathology. RESULTS: A total of 58 patients underwent radial EUS and 31 patients underwent linear EUS examination. There were 38 lesions correctly diagnosed in the radial EUS group and 29 correctly diagnosed lesions in the linear EUS group. The diagnostic accuracy of SMd invasion for linear EUS was significantly higher than radial EUS (0.936 vs. 0.655, p = 0.003). A significant difference was also noted for specificity between the two groups (0.963 vs. 0.659, p = 0.003). Univariate analysis showed radial EUS type (OR 0.131, 95% CI 0.028-0.606, p = 0.009) to be an independent predictor for incorrect diagnosis. The area under the receiver operating curve (ROC) was 0.856 and 0.651 for linear EUS and radial EUS, respectively. It was noted that four patients underwent unnecessary surgery for radial EUS while there were no such patients in the linear EUS group. CONCLUSIONS: Linear EUS was more accurate for determining SMd invasion and contributed to the selection of appropriate treatment modalities in patients with non-pedunculated rectal polyp.