Bowel Prep for Colorectal Surgery: Which Is the Most Effective?

Albert B. Lowenfels, MD


May 22, 2018

What is the most effective and safest method of bowel preparation prior to surgery of the large bowel? To answer this question, the authors of a study published in Annals of Surgery examined records (N = 32,359) of patients who underwent large bowel procedures in the American College of Surgeons National Surgery Quality Improvement Program database over a 2-year period (2012-2014).[1]

Patients were divided into four groups:

  • No bowel preparation: 26.7%

  • Only mechanical bowel prep (MBP): 36.6%

  • Only oral antibiotics (OA): 3.8%

  • MBP and OA: 32.9%

The primary endpoint was any surgical-site infection within 30 days after surgery. The combination of MBP and OA significantly reduced the risk for any surgical-site infection (adjusted OR, 0.49; 95% CI, 0.43-0.54; P < .001) There were significant reductions in other endpoints, such as anastomotic leaks (P < .001), postoperative ileus (P < .001), and fewer returns to the operating room (P < .001).


This retrospective study, based on information from 203 participating centers, demonstrates a benefit from MBP and OA for patients undergoing elective colorectal surgery. This was not a randomized controlled trial, so the authors used propensity matching in an attempt to overcome patient differences in the various groups.

Although a true randomized trial might provide more accurate information, the 50% reduction in surgical infection rate with a combination of MBP and OA is impressive. Some authors have documented an increase of Clostridium difficile infection with use of oral bowel preps, but such information was unavailable in this dataset. The authors concluded that until other data become available, MBP + OA should now be the standard of care for patients undergoing bowel surgery.

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