BACKGROUND: The aim of this study was to evaluate the effects of preoperative mechanical bowel preparation (MBP) on colonic ischemia/reperfusion (I/R) injury. METHODS: Seventy adult male Sprague-Dawley rats were divided randomly into 7 equal groups of 10 rats each. Groups were assigned as follows: group I = sham surgery; group II = I/R of left colon (control group); group III = intravenous heparin and metronidazole followed by I/R of the left colon; groups IV through VII = before I/R of the left colon, heparin and metronidazole and MBP were performed with sodium chloride (NaCl), Na phosphate, polyethylene glycol, and mannitol, respectively. Histopathogic and biochemical parameters were evaluated. RESULTS: According to the histopathologic changes, the groups least affected by I/R injury were groups V and VII. Catalase activity was significantly higher in groups V and VII, and copper-zinc superoxide dismutase activity was significantly higher in group VII compared with the control group (P <.002). CONCLUSIONS: MBP with sodium phosphate and mannitol appears to be more protective against I/R injury. (c) 2008 Elsevier Inc. All rights reserved.