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Database of Abstracts of Reviews of Effects (DARE): Quality-assessed Reviews [Internet]. York (UK): Centre for Reviews and Dissemination (UK); 1995-.

Database of Abstracts of Reviews of Effects (DARE): Quality-assessed Reviews [Internet].

Updated systematic review and meta-analysis of randomized clinical trials on the role of mechanical bowel preparation before colorectal surgery

K Slim, E Vicaut, MV Launay-Savary, C Contant, and J Chipponi.

Review published: 2009.

Link to full article: [Journal publisher]

CRD summary

This review concluded that there was a high level of evidence that any kind of mechanical bowel preparation should be omitted before colonic surgery, although the analysis did not confirm a harmful effect of mechanical bowel preparation. The authors' conclusions seem reasonable and are likely to be reliable.

Authors' objectives

To evaluate the role of mechanical bowel preparation in colorectal surgery and the influence of different preparation regimes on infection outcomes.


MEDLINE, the Cochrane Library and Scopus were searched up to January 2008, as well as the last six issues of major surgical journals, the proceedings of major meetings from 2004 and the reference lists of retrieved articles. Search terms were not reported. This search updated searches from an earlier review on the topic (see Publications of Related Interest). Based on the earlier publication, there were no language restrictions.

Study selection

Randomised controlled trials (RCTs) that compared mechanical bowel preparation with no mechanical bowel preparation before elective colorectal surgery were included. The primary outcome of interest was anastomotic leakage. Secondary outcomes were infectious complications (pelvic abscess, peritonitis, wound infection), overall surgical site infection, re-operation, extra-abdominal infectious complications, length of hospital stay and death.

The included studies used the following solutions: polyethylene glycol, sodium phosphate, mannitol or magnesium phosphate mechanical bowel preparation. The majority of trials defined the comparator as 'no additional bowel' or 'rectal cleansing'. Most trials were of adults, with the exception of one trial that also included children. All trials confirmed anastomic leakage based on a clinically suspected leak.

Two researchers independently selected studies for inclusion.

Assessment of study quality

Trials were assessed for reporting of randomisation, allocation concealment, single blinding (double blinding was considered not feasible) drop-out and withdrawals. The maximum possible score was 5 points; trials with a score of 2 or less were classified as poor quality.

Validity assessment was undertaken independently by two researchers and disagreements were resolved through consensus.

Data extraction

Two researchers independently extracted data. The number of events for the outcomes of interest and the number randomised were extracted and the odds ratio (OR) and 95% confidence interval (CI) calculated. Authors were contacted for additional data where necessary.

Methods of synthesis

Trials were pooled in a meta-analysis using a Peto random-effects model. Statistical heterogeneity was assessed using the Q-statistic and I2. Subgroup analyses were undertaken to assess the robustness of the results based on poor quality versus good quality studies; large (two trials of over 1,300 participants each) versus small trials; polyethylene glycol versus other solutions; and peritoneal versus infraperitoneal anastomosis. A funnel plot for the primary outcome was visually inspected to assess for the possibility of publication bias.

Results of the review

Fourteen RCTs (n=4,859 patients) were included. Three RCTs had a quality score of 2 points and were classified as poor quality; the remaining trials scored 3 or, most commonly, 4 points. Excluding the two large trials of more than 1,300 participants each, sample size ranged from 47 to 380. Where reported, length of follow-up ranged from seven to 90 days.

Following mechanical bowel preparation, 4.02% of participants experienced anastomotic leakage compared with 3.44% of participants without mechanical preparation. There was no statistically significant difference in anastomotic leakage between the two groups (OR 1.12, 95% CI: 0.82 to 1.53, 14 trials). There was no statistically significant difference between groups for the other outcomes, except for overall surgical site infections, where there was a higher risk in the mechanical bowel preparation group (OR 1.40, 95% CI: 1.05 to 1.87, 14 trials). There was statistically significant heterogeneity in this analysis. The subgroup analyses did not substantially alter the results. It was not possible to undertake subgroup analysis of rectal surgery as, for the majority of trials, this was an exclusion criterion in the trial or data were not reported separately for this group.

The authors stated that visual inspection of the funnel plot did not suggest publication bias, but interpretation was limited by the small number of trials.

Authors' conclusions

Although it did not confirm a harmful effect of mechanical bowel preparation, the analysis demonstrated a high level of evidence that any kind of mechanical bowel preparation should be omitted before colonic surgery.

CRD commentary

This review had clearly stated inclusion criteria and a number of relevant sources were searched for studies, including possible sources of unpublished data. Appropriate methods were used to reduce error and bias in the review processes.

Study quality was assessed and considered in the analysis. The approach to the analysis seemed appropriate and heterogeneity was assessed and investigated.

The authors' conclusions seem appropriate and are likely to be reliable.

Implications of the review for practice and research

Practice: The authors state that mechanical bowel preparation should not be used before colonic surgery.

Research: The authors stated that evaluation is required of the role of mechanical bowel preparation in rectal surgery.


Not stated

Bibliographic details

Slim K, Vicaut E, Launay-Savary MV, Contant C, Chipponi J. Updated systematic review and meta-analysis of randomized clinical trials on the role of mechanical bowel preparation before colorectal surgery. Annals of Surgery 2009; 249(2): 203-209. [PubMed: 19212171]

Other publications of related interest

Slim K, Vicaut E, Panis Y, Chipponi J. Meta-analysis of randomized clinical trials of colorectal surgery with or without mechanical bowel preparation. British Journal of Surgery 2004;91(9):1125-1130.

Indexing Status

Subject indexing assigned by NLM


Anastomosis, Surgical /adverse effects; Cathartics /administration & dosage /adverse effects; Colectomy /adverse effects; Colon /surgery; Humans; Postoperative Complications /etiology /prevention & control; Preoperative Care; Randomized Controlled Trials as Topic; Rectum /surgery; Surgical Wound Infection /etiology /prevention & control



Database entry date


Record Status

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.

CRD has determined that this article meets the DARE scientific quality criteria for a systematic review.

Copyright © 2014 University of York.

PMID: 19212171


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