Background: The presence of bowel contents during surgery has been related to anastomotic leakage, but the belief that mechanical bowel preparation (MBP) is an efficient agent against leakage and infectious complications is based on observational data and expert opinions only.
Objectives: To determine the security and effectiveness of MBP on morbidity and mortality in colorectal surgery.
Search strategy: Publications describing trials of MBP before elective colorectal surgery were sought through searches of MEDLINE, EMBASE, LILACS, and The Cochrane Library; by handsearching relevant medical journals and conference proceedings, and through personal communication with colleagues.Searches were performed March 13, 2008.
Selection criteria: Randomised controlled trials (RCTs) including participants submitted for elective colorectal surgery. Eligible interventions included any type of MBP compared with no MBP. Primary outcomes included anastomosis leakage - both rectal and colonic - and combined figures. Secondary outcomes included mortality, peritonitis, reoperation, wound infection, extra-abdominal complications, and overall surgical site infections.
Data collection and analysis: Data were independently extracted and checked. The methodological quality of each trial was assessed. Details of randomisation, blinding, type of analysis, and number lost to follow up were recorded. For analysis, the Peto-Odds Ratio (OR) was used as the default (no statistical heterogeneity was observed).
Main results: Four new trials were included at this update (total 13 RCTs with 4777 participants; 2390 allocated to MBP (Group A), and 2387 to no preparation (Group B), before elective colorectal surgery) .Anastomotic leakage occurred:(i) in 10.0% (14/139) of Group A, compared with 6.6% (9/136) of Group B for low anterior resection; Peto OR 1.73 (95% confidence interval (CI): 0.73 to 4.10).(ii) in 2.9% (32/1226) of Group A, compared with 2.5% (31/1228) of Group B for colonic surgery; Peto OR 1.13 (95% CI: 0.69 to 1.85). Overall anastomotic leakage occurred in 4.2% (102/2398) of Group A, compared with 3.4% (82/2378) of Group B; Peto OR 1.26 (95% CI: 0.941 to 1.69). Wound infection occurred in 9.6% (232/2417) of Group A, compared with 8.3% (200/2404) of Group B; Peto OR 1.19 (95% CI: 0.98 to 1.45). Sensitivity analyses did not produce any differences in overall results.
Authors' conclusions: There is no statistically significant evidence that patients benefit from MBP. The belief that MBP is necessary before elective colorectal surgery should be reconsidered. Further research on patients submitted for elective colorectal surgery in whom bowel continuity is restored, with stratification for colonic and rectal surgery, is still warranted.