Screening of asymptomatic patients at risk is potentially the most effective means for detecting early colorectal carcinoma. Sensitive and specific tests are available for this purpose. However, an aggressive approach by the physician and compliance by the patient population are necessary for the proper implementation of this screening process.

Delivery of 10% carrageen (degraded carrageenan, Glaxo, France) for 10 days in the drinking water to CF₁ mice induced bloody diarrhea, pericryptal inflammation, and marked dilatation of the cecum and ascending colon. Histologically, the mucosa was characterized by distorted crypt architecture, inflammatory infiltration of the lamina propria, and ulceration, conditions which were more pronounced in the proximal colon but were also present in the distal colon. Treatment with hydrocortisone and levamisole reduced the severity of all phases of the reaction. Alterations in colonic epithelial cell proliferation corresponded with the clinical and histopathological findings. Labeling indices (LI) significantly increased over control values in both proximal (12.9 ± 4.9 vs. 7.6 ± 2.9) and distal colon (13.9 ± 5.2 vs. 7.2 ± 2.4), effectively doubling the number of proliferating cells per crypt column in both areas. However, DNA-synthesizing cells extended further upward along the cryptal wall of the proximal colon reflecting greater mucosal damage. Only in the proximal colon did the proliferative compartment (PC) extend to the upper third of the glands, normally not a proliferative zone. Hydrocortisone and levamisole administered concurrently with 10% carrageen were less effective in protecting the proximal colon since LI and numbers of labeled cells per crypt column were consistently lower in the distal colon. Moreover, hydrocortisone alone significantly depressed DNA synthesis only in the distal colon. All distal colonic crypts were not equally protected by administration of hydrocortisone since some continued to express large numbers of proliferating cells and an extended PC, well characterized preneoplastic defects in regulatory control of colonic epithelial cell proliferation. The clinical presentation, histopathology, proliferative alterations, potential premalignancy, and response to pharmaceutic intervention of carrageen-induced colitis in mice support its continued investigation as an animal model for human ulcerative colitis.

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