Colonic stenoses: use of oral barium when retrograde flow is completely obstructed on barium enema studies. Forty patients with complete obstruction to retrograde barium flow on barium enema examinations, without clinical or radiographic evidence of obstruction, were studied further with orally administered barium in the same session. All patients had undergone aborted double-contrast barium enema studies and had received antispasmodics intramuscularly before the examination. The authors describe the technique, as well as the clinical and radiologic findings, that allows the safe ingestion of oral barium in patients with stenotic lesions of the colon. In all patients, oral barium passed through the small bowel and the stenotic site in an average of 148 minutes, with no complications. In seven patients, there were synchronous lesions in the colon and small bowel, and the findings were determined better with oral barium studies in 19 patients. If a barium enema study is done and retrograde passage of barium is obstructed by a lesion in the left side of the colon, additional diagnostic information can be obtained by giving the patients oral barium. This practice is safe if precise criteria are applied. 