Systemic prophylaxis with metronidazole (Flagyl) in elective surgery of the colon and rectum.

The effect of metronidazole prophylaxis in elective colonic and rectal surgery was studied in a prospective double-blind trial in which metronidazole was compared with a placebo. Fifty-six patients were included in the study, and the patients were randomly allocated to the two groups. Twenty-five patients received 2 gm of metronidazole the day before operation and 1.2 gm as a single daily dose for 5 days after operation. Twenty-one patients were given placebos in the same dosage. Before operation all patients were prepared with mechanical evacuation of the bowel. A significantly lower frequency of wound spesis, intraabdominal complications, and septicemia was found in the metronidazole group as compared to the placebo group. The incidence was 4.0% and 36%, respectively. Following protectomy, infection in the perineal area occurred in 33% and 43% of the respective groups. In the metronidazole-treated patients, however, this was the only complication, whereas 50% of the patients in the placebo group developed intraabdominal complications as well. After operation anaerobic bacteria were isolated from 8% of the patients who received prophylactic metronidazole. In the control group 67% of the patients had a positive postoperative anaerobic culture. Bacteroides fragilis was isolated from 13 of 14 patients with postoperative infection in the placebo group. B. fragilis was not isolated from any of the metronidazole-treated patients. The study indicates that anaerobic bacteria are the major contributors to would infection following colonic and rectal surgery and that metronidazole prophylaxis greatly reduces the frequency of postoperative infection.