Chewing Gum Reduces Postoperative Ileus Following Abdominal Surgery

A Meta-analysis of 17 Randomized Controlled Trials

Shan Li; Yanqiong Liu; Qiliu Peng; Li Xie; Jian Wang; Xue Qin


J Gastroenterol Hepatol. 2013;28(7):1122-1132. 

In This Article


We attempted to follow the proposals Quality of Reports of Meta-Analyses of Randomized Controlled Trials: the QUOROM statement to report our meta-analysis.[38]

Search Strategy

Electronic databases MEDLINE, EMBASE, and Cochrane Library were used to search for RCTs up to December 2012. The final search strategy used for each database was based on key words both alone and combinations of the terms "chewing gum" and "surgery." A manual search of the reference lists of relevant articles was performed. A systematic search of Google Scholar was used to explore the gray literature. No language or time restrictions were made. Two reviewers (Yanqiong Liu and Li Shan) independently evaluated all retrieved articles using prespecified eligibility criteria. Disagreements were resolved by consensus. When a study reported the results on different indication of surgery, we treated it as separate studies in the meta-analysis.

Eligibility Criteria

Studies were considered eligible if they met the following inclusion criteria: (i) Study design: randomized and controlled; (ii) Population: patients undergoing abdominal surgery; (iii) Intervention: use of chewing gum in the postoperative period; (iv) Comparator: standard postoperative care; (v) Outcome: report at least one of time to flatus, time to bowel movement, and hospital LOS. We did not use an age criterion and any minimum number of patients for inclusion in this meta-analysis.

Studies were excluded if any of the following existed: (i) nonrandomized study design; (ii) surgeries that did not involve abdominal surgery; (iii) primary outcome was not the interest of ours; (iv) interventions other than chewing gum; (vi) raw data could not be extracted in the appropriate format and failed to be obtained from the authors or other published results.

Data Extraction

Information was carefully extracted from all eligible publications by two investigators (Li Shan and Yanqiong Liu) independently according to the inclusion criteria listed earlier. Any disagreements were resolved by discussion during a consensus meeting with a third reviewer (Qin Xue). The data extracted included first author's last name, year of publication, country, type and indication of surgery performed, total numbers of cases and controls, patient demographics for treatment and control groups (e.g. gender distribution, mean age), duration of operation time, time of gum chewing, rate of complications, quality indicators (e.g. details of randomization, blinding of patients), time to flatus, time to bowel movement, and LOS for treatment and control groups.

Risk of Bias Assessment

The risk of bias of each eligible study was assessed by two authors (Yanqiong Liu & Shan Li) using the Cochrane Risk of Bias tool[39] for RCTs. Disagreements were discussed with a third author (Xue Qin) and resolved by consensus. The instruments are described in detail elsewhere.[39]

Statistical Analysis

Weighted mean differences (WMDs) together with their corresponding 95% confidence intervals (CIs) were estimated using a random-effects model.[40] Statistical heterogeneity was assessed by visual inspection of forest plots, by performing the χ2 test (assessing the P-value) and by calculating the I2 statistic.[41,42] If the P-value was less than 0.10 and I2 exceeded 50%, indicating the presence of heterogeneity, a random-effects model (the DerSimonian and Laird method) was used;[43] otherwise, the fixed-effects model (the Mantel and Haenszel method) was used.[44] Publication bias was evaluated by constructing a funnel plot with visual assessment of asymmetry.[45,46] Subgroup analyses were carried out to examine whether the duration of POI varied by type of surgery, the indication of surgery, or Jadad quality. Sensitivity analysis was also performed to examine whether the effect estimate was robust to exclusion of different criterion. Cumulative meta-analysis was conducted to examine how the evidence has changed over time. A P-value < 0.05 was considered statistically significant. All analyses were performed using STATA version 12.0 (StataCorp LP, College Station, TX, USA).