The clinical significance of colorectal flat lesions under endoscopy

Abstract

To identify flat lesion in colon and rectum with combination of magnifying endoscope and mucosa staining technique ad to compare the differences between the protruded and flat colorectal lesions. 16 457 consecutive patients with colorectal lesions underwent magnifying endoscopy and mucosa staining to detect protruded and flat colorectal lesions. The clinical data were analyzed. (1) A total of 1472 adenoma cases were found; 154 (10.46%) of which were of the flat type. (2) The average size of flat adenoma was (17 +/- 14) mm, significantly smaller than that of polypoid adenoma [(29 +/- 9) mm, P < 0.05)]. (3) The incidence of colorectal tumor in the left colon was 82.35% (140/170) in the flat type tumor, significantly higher than that in the protruded type tumors (79.59%, 1630/2048, P = 0.013). (4) The incidence rates of tubular adenoma, tubulo-villous adenoma, villous adenoma, and cancer were 51.34%, 4.25%, 8.79%, and 35.65% respectively in the protruded type tumor, and were 55.55%, 17.06%, 17.64%, and 9.43% respectively. The detection rates of mild, moderate, and severe dysplasia and early cancer were 31.15%, 16.46%, 2.20%, and 2.39% respectively in the protruded type tumor, and were 25.88%, 20.00%, 9.41%, and 8.62% respectively in the flat type tumor. The detection rates of moderate and severe dysplasia and early colorectal cancer in the flat adenomas are higher than in the protruded adenoma. Of higher malignancy grade, flat adenomatous lesions are more likely to be carcinomatous compared with the protruded adenomatous lesions.