Before surgical resection of the colon and/or rectum, we propose: 1) mechanical preparation of the intestine using X prep Sarget (1 pack, 120 mg, diluted in water or two packs in case of obesity) and an antiseptic (iodine polyvidone) (two 2-liter enemas at 5%, one the day before surgery and one 2 hours prior to surgery) associated with; 2) bitherapy (1 g dose of ceftriaxone plus 1 g ornidazole or metronidazole diluted in 125 mg saline solution, for 15 minutes) administered parenterally at least half an hour before the skin incision.