Endoscopic and radiographic evaluation of the murine colon. Endoscopic and radiographic techniques have not been widely applicable in the evaluation of chemically induced murine colon cancer. The authors investigated methods of cleansing the rat colon and refined endoscopic and radiographic techniques. They compared total colonoscopy (TC) and air-contrast (ACBE) and single-contrast barium enema (SCBE) findings with those obtained at necropsy in rats with 1,2-dimethylhydrazine (DMH)-induced colon cancer. Gastrograffin enemas with bisacodyl suppositiories showed complete evacuation of solid feces. Sprague-Dawley rats treated with DMH had their colons cleansed and then underwent TC (5.0-mm Olympus bronchoscope) and either SCBE or ACBE. Colonoscopy and ACBE were equally sensitive (81.5% and 76.3%, respectively), although SCBE was significantly insensitive in identifying lesions (P less than 0.001). This study demonstrates that: (1) mechanical cleansing of the rat colon is feasible, (2) TC and barium radiology can be done routinely after mechanical cleansing, and (3) TC and double-contrast BE are sensitive in identifying colon lesions. These techniques will provide a means for manipulation of murine tumors and in vivo surveillance. 