Clinical course and magnifying endoscopic findings of fine lesions of the large intestinal mucosa in Crohn's disease.

"Worm-eaten" appearance (WEA) is a fine lesion of Crohn's disease observed in apparently normal rectal mucosa by magnifying endoscopy. Magnifying endoscopy has now been performed following application of methylene blue on 37 occasions in 27 patients with Crohn's disease, and the occurrence of WEA was reviewed in relation to the duration and extent of disease. The frequency of WEA was 75% in patients with a history of less than five years and 77% in those who had had the disease for more than five years. In the active stage, the frequency was 85% and 100% respectively, and the degree of WEA also increased. The detection rate of granulomata in regions of WEA was 53% when the clinical history was less than five years and 33% when five years or more. In active disease, granulomata were found in 70% and 67% respectively. The large intestine other than the rectum was reviewed in eight patients with ileitis. WEA and granulomata were observed throughout the large intestine including the cecum, especially when the ileal disease was active.