Radiological evaluation of rat colonic tumors.

Colon carcinomata were induced in rats with N-methyl-N-nitro-N-nitrosoguanidine. A magnified double contrast barium enema technique was developed for an in vivo study of tumor growth patterns. Invariably, all small tumors were smoothly outlined and were spherical or ellipsoidal in shape. Irregularity developed only when the tumors grew larger, at which time there was considerable variation in the tumor growth patterns. The onset, shape, progression, spread and number of tumors present can be studied without sacrificing the animal.