Meta-analysis of randomized clinical trials of colorectal surgery with or without mechanical bowel preparation

Background: Mechanical bowel preparation is used routinely before colorectal surgery, but some randomized clinical trials have suggested that it is of no benefit. This study assesses whether such bowel preparation may safely be omitted before elective colorectal surgery. Methods: A search of the literature was performed; the inclusion criteria were randomized clinical trials comparing bowel preparation with no preparation in colorectal surgery. The methodological quality of included trials was assessed. The primary outcome was anastomotic leakage; secondary outcomes were other septic complications. The meta-analysis was conducted using the Peto one-step method. Results. Eleven trials were retrieved, of which seven, containing 1454 patients, were included in the meta-analysis. There was no heterogeneity between the trials. Significantly more anastomotic leakage was found after mechanical bowel preparation (5-6 versus 3.2 per cent; odds ratio 1.75 (95 per cent confidence interval 1.05 to 2.90); P = 0-032). All other endpoints (wound infection, other septic complications and non-septic complications) also favoured the no-preparation regimen, but the differences were not statistically significant. Sensitivity analysis showed that these results were similar when trials of poor quality were excluded. Subgroup analysis showed that anastornotic leakage was significantly greater after bowel preparation with polyethylene glycol (PEG) compared with no preparation, but not after other types of preparation. Conclusion: There is good evidence to suggest that mechanical bowel preparation using PEG should be omitted before elective colorectal surgery. Other bowel preparations should be evaluated by further large randomized trials.