Original article Mechanical bowel preparation does not influence outcomes following colonic cancer resection G. A. Nicholson 1 , I. G. Finlay 2 , R. H. Diament 3 , R. G. Molloy 4 , P. G. Horgan 5 and D. S. Morrison 1 1 West of Scotland Cancer Surveillance Unit, Section of Public Health and Health Policy, Faculty of Medicine, University of Glasgow, and 2 Department of Surgery, Glasgow Royal Infirmary, Glasgow, 3 Department of Surgery, Crosshouse Hospital, Kilmarnock, 4 Department of Surgery, Gartnavel General Hospital, and 5 Department of Academic Surgery, Glasgow Royal Infirmary, Glasgow, UK Correspondence to: Mr G. A. Nicholson, West of Scotland Cancer Surveillance Unit, Section of Public Health and Health Policy, Faculty of Medicine, University of Glasgow, 1 Lilybank Gardens, Glasgow G12 8RZ, UK (e-mail: garynicholson@nhs.net) Background: Meta-analyses have indicated that preoperative mechanical bowel preparation (MBP) confers no clear benefit and may indeed be harmful for patients with colorectal cancer. The effects of bowel preparation on longer-term outcomes have not been reported. The aim was to compare long-term survival and surgical complications in patients who did or did not receive MBP before surgery for colonic cancer. Methods: This was a retrospective cohort study of all patients undergoing potentially curative surgery for colonic cancer after routine hospital admission in the West of Scotland between January 2000 and December 2005. Clinical audit data were linked to cancer registrations and death certificates. Kaplan–Meier and Cox proportional hazards models were used to explore determinants of survival. Results: A total of 1730 patients underwent potentially curative surgery for colonic cancer, of whom 886 (51·2 per cent) were men. The mean(s.d.) age was 69·7(10·6) years. Some 1460 patients (84·4 per cent) received MBP. Median follow-up was 3·5 (range 0·1–6·7) years. There were no statistically significant differences in 30-day postoperative complication rates between groups. The unadjusted hazard ratio (HR) for death from all causes for patients treated with MBP (versus no MBP) was 0·72 (95 per cent confidence interval 0·57 to 0·91). Multivariable analysis with adjustment for age, sex, socioeconomic circumstances, disease stage and presentation for surgery showed that MBP had no independent effect on all-cause mortality (HR 0·85, 0·67 to 1·10). Conclusion: Neither postoperative complications nor long-term survival are improved by MBP before colonic cancer surgery. Paper accepted 7 January 2011 Published online 15 March 2011 in Wiley Online Library (www.bjs.co.uk). DOI: 10.1002/bjs.7454 Introduction Mechanical bowel preparation (MBP) has been used routinely in colorectal surgery, with the aim of reducing postoperative complications 1–3 . However, recent system- atic reviews and meta-analyses of randomized controlled trials (RCTs) have consistently found no convincing evi- dence for its short-term benefits 2–7 , and some evidence for a lower rate of postoperative cardiac events among patients who did not receive MBP 8 . Subsequent to their Cochrane review in 2005 2 , in their latest update Guenaga and colleagues 7 reported that the incidence of anastomotic leakage was significantly higher among patients treated with MBP and that there was a trend towards poorer short-term outcomes. It should be noted that the primary outcome for the Cochrane review was anastomotic leakage and the majority of included studies followed patients for the postoperative period (30 days after surgery), the longest follow-up being about 2 months 9 . There is accumulating evidence that operative compli- cations predict long-term outcomes, specifically survival, in patients with colorectal cancer. Anastomotic leak- age is an independent prognostic indicator of poorer cancer-specific survival after potentially curative resec- tion and remains significant after exclusion of deaths within the postoperative period 10–12 . However, no study on MBP with longer follow-up has been reported. It might  2011 British Journal of Surgery Society Ltd British Journal of Surgery 2011; 98: 866–871 Published by John Wiley & Sons Ltd