Endoscopic appearances of the rectal mucosa of patients with Crohn's disease visualised with a magnifying colonoscope.

The magnified endoscopic appearances of the rectum are described in 12 patients with Crohn's disease with apparent rectal sparing on sigmoidoscopy. Five of them had minor abnormalities on colonoscopy but the remaining seven had a normal rectum. After the application of 0.2% methylene blue, examination using a magnifying endoscope (Olympus CF-HM) revealed characteristic 'worm-eaten' appearances in 75% of the patients regardless of the activity of their disease. Histological examination of biopsy specimens from these lesions showed marked inflammatory changes, and granulomas or microgranulomas were found in 75%. Inflammatory changes were not seen in mucosa which appeared normal on magnifying colonoscopy although microgranuloma were found in three cases. These observations confirm the focal nature of Crohn's disease and may suggest that the early lesions are mucosal and frequently contain granulomata.