Mechanical bowel preparation with oral antibiotics may be the best approach to reducing surgical site infections in patients undergoing colorectal surgery, according to a study recently published in JAMA Network Open.

The use of mechanical bowel preparation and oral antibiotics before elective colorectal surgery is a currently controversial topic because of the diverse reported outcomes. Although the American Society for Enhanced Recovery and the Perioperative Quality Initiative joint consensus statement recommends the “routine use of a combined isosmotic mechanical bowel preparation with oral antibiotics before elective [colorectal surgery]” to reduce surgical site infection, international guidelines in the United States, Europe, and Asia-Pacific lack consensus; recent Australian guidelines recommend that “mechanical bowel preparation should not be used routinely in colonic surgery.” 

Further, a recent survey of European colorectal surgeons found that despite recent evidence that preoperative oral antibiotics may reduce surgical site infection, few European surgeons used such treatment. Previous meta-analyses have only provided comparisons between 2 approaches, which has made it difficult to compare all the results. Therefore, to compare all 4 approaches simultaneously (mechanical bowel preparation with oral antibiotics, oral antibiotics only, mechanical bowel preparation only, or no preparation), a network meta-analysis was performed and aimed to clarify which approach in colorectal surgery is associated with the lowest rate of surgical site infection.

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A total of 38 randomized clinical trials were identified and included through 5 electronic database searches and reference lists. In total, 8458 patients (52.1% male) were included; there were 17 studies identified comparing mechanical bowel preparation vs no preparation (2117 vs 2128 patients), 3 studies identified comparing mechanical bowel preparation with oral antibiotics vs oral antibiotics only (349 vs 344 patients), and 19 studies identified comparing mechanical bowel preparation with oral antibiotics vs prep only (1831 vs 1731 patients). This network meta-analysis made 4 direct comparisons (mechanical bowel preparation with oral antibiotics vs prep alone, mechanical bowel preparation with oral antibiotics vs antibiotics alone, mechanical bowel preparation vs no preparation, and mechanical bowel preparation vs oral antibiotics) and 2 indirect comparisons (mechanical bowel preparation with oral antibiotics vs no preparation and antibiotics vs no preparation). The primary measure was total, incisional, and organ/space surgical site infection rates. Quality of studies was appraised by the Cochrane Collaboration risk of bias tool.

Results demonstrated that there was no benefit of mechanical bowel preparation only compared with no preparation (odds ratio [OR}, 0.84; 95% equal-tail credible interval, 0.69-1.02), and there was no significant different between mechanical bowel preparation with oral antibiotics vs antibiotics alone. Conversely, there was a statistically significant reduction in total surgical site infection for mechanical bowel preparation with oral antibiotics compared with mechanical preparation only ( OR, 0.71, 95% equal-tail credible interval, 0.57-0.88). Further, there was a statistically significant improvement in total surgical site infection and incisional surgical site infection when mechanical bowel preparation with oral antibiotics was used compared with mechanical bowel preparation. The odds ratio for organ/space surgical site infection was 0.72. Mechanical bowel preparation with oral antibiotics consistently ranked as the best regimen in 4 of 8 outcome measures, and second best in 2 of 8 outcome measures, including being associated with a statistically significant reduction in organ/space surgical site infection. However, there was no difference in rates of anastomotic leak, readmissions, or reoperations between any groups.

Overall, the study authors concluded that, “The long-standing practice of [mechanical bowel preparation] and no preparation is still a common approach and should be revisited after careful reconsideration of the growing body of evidence from [random clinical trials] and population-based studies.”

Reference

Toh JW, Phan K, Pathma-Nathan N, et al. Association of mechanical bowel preparation and oral antibiotics before elective colorectal surgery with surgical site infection. A network meta-analysis. JAMA Netw Open. 2018;1(6):e183226.