Endoscopic diagnosis of chemically induced autochthonous colonic tumors in rats.

The suitability of using coloscopy as a diagnostic method is investigated with respect to colonic carcinomas induced locally by the administration of N-nitrosoacetoxymethyl-methylamine, N-methyl-N-nitrosourea, and methylnitro-nitrosoguanidine, or systemically by subcutaneous injection of 1,2-dimethylhydrazine in Sprague-Dawley rats. The endoscopic diagnostic examination proved to be clearly superior to methods of animal inspection, palpation, investigation for occult blood and exploratory laparotomy which have so far been employed in animal experiments with small rodents. The relevance of this method is discussed for the early detection of chemically induced colonic tumors, and the observation of tumor development under experimental cytostatic therapy.