Four patients with partial obstruction of the colon, in whom adequate standard preparation for colonic resection was not possible, are presented. Clinically, these patients did not show sufficient signs of obstruction to require a preliminary colostomy. A technique of quarantining the area of tumor resection from the abdominal cavity is described, allowing for adequate preparation of the colon lumen at the site of anastomosis. After completion of the anastomosis, a large caliber (36 French) colonic tube is inserted, per rectum, through the anastomosis and the proximal colon irrigated with Betadine solution adequately emptying and sterilizing the lumen of the bowel to allow for primary anastomosis without a protective colostomy. The criteria for selection of patients for this technique are discussed. No complications, of significance, ensued. This method of intraoperative rectal tube irrigation, for prevention of colostomy in partial colonic obstruction, is safe when properly performed in the appropriate patient.