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Editor,—We read with great interest the article by Martin et al (Gut1999;45:147) on normal histological findings in small depressed lesions of the large bowel. They described three patients with 7–8 mm depressed rectal lesions, similar to small flat or depressed neoplastic lesions, during sigmoidoscopy (two cases) and total colonoscopy (one case). Specimens taken by extensive biopsy or removed by endoscopic mucosectomy were histologically normal with no evidence of neoplasia. Two weeks later, colonoscopy with chromoscopy in one patient failed to locate the lesion. In contrast to true flat adenomas characterised by rough, reddened central mucosa and an irregular outline, the lesions had normal central mucosa and a regular circular elevation. The authors therefore concluded that flat lesions with a regular circular shape and normal central mucosa are likely to be of little significance, and recommended diagnostic cold biopsy in these cases.
Despite their claim of the first report of normal histological findings in small depressed lesions, we had described similar lesions as ring-like elevations.1 Histological assessment of biopsy and endoscopic mucosectomy specimens of the elevations revealed slight oedema within the lamina propria. Whereas we observed such elevations predominantly in the ascending colon, their lesions were seen in the rectum. Because cleansing preparation fluid tends to be retained often in the ascending colon and rectum, requiring frequent aspiration, we suspect that their lesions are also pseudolesions caused by suction of the mucosa into a colonoscope forming ring-like elevations.1 Although they mentioned that suction had not been applied to the mucosa, experienced endoscopists usually aspirate retained fluid unconsciously during colonoscopy. Although histological findings of their lesions showed normal mucosa, we suspect that slight oedema was probably present within the lamina propria of their ring-like lesions. We believe their lesions are the same as ring-like elevations.
Some diminutive polyps disappear during maximal colonoscopic insufflation. This phenomenon is invariably associated with hyperplastic polyps, but not with adenomas.2 Dye-spraying techniques readily visualise the innumerable fine grooves, the so-called innominate grooves, which remain visible in non-neoplastic lesions and in normal colonic mucosa, but not in neoplastic lesions.3 Because ring-like elevations usually disappear after vigorous air insufflation and the innominate grooves are always visualised in the elevations, the disappearing phenomenon and the presence of innominate grooves in the lesions serve to differentiate this artefact from true neoplastic lesions.1 With these endoscopic signs, we can avoid biopsy or removal, and thus the cost of pathological examinations.
Editor,—We value the comments made by Matsushitaet al and are grateful to them for bringing to our attention their earlier letter which reports ring-like elevations of the colon thought to be due to suction artefacts.1-1 Although we agree with their points regarding the use of suction by experienced colonoscopists, we believe it is unlikely that the lesions we reported were suction related. All of our lesions were initially visualised in the distance, away from the colonoscope tip, and showed no signs of mucosal trauma such as spotted haemorrhage, on close inspection. In addition, there was no histological evidence of increased mucosal oedema to suggest suction trauma.
Maximum air insufflation and observation of these lesions over several minutes was performed routinely, and a striking feature noted was their “fixed nature”. We agree that if a normal groove pattern is seen following dye spray and the lesion disappears after air insufflation, then biopsy is unnecessary. However, if lesions fail to disappear, as in the cases we reported, some doubt must remain regarding their nature. In this situation biopsy seems a safe precaution, particularly given the relatively high incidence of advanced neoplasia in true flat adenomas.