Effect of preoperative oral antibiotics in combination with mechanical bowel preparation on inflammatory response and short-term outcomes following left-sided colonic and rectal resections.

Preoperative oral antibiotics in addition to intravenous antibiotics and mechanical bowel preparation (MBP) may influence the gut microbiome and reduce both the postoperative systemic inflammatory response to surgery and postoperative infective complications following colorectal resection. This propensity score-matched study compared outcomes of patients undergoing left-sided colonic or rectal resection with or without a combination of oral antibiotics and MBP.

The addition of oral antibiotics and MBP to prophylactic intravenous antibiotics in left-sided colonic and rectal resections was introduced in 2015-2016 at a single institution. Propensity score matching was undertaken to compare the effects of oral antibiotics plus MBP versus neither oral antibiotics nor MBP on the postoperative systemic inflammatory response and short-term outcomes in patients undergoing left-sided colonic or rectal resection between 2013 and 2018.

Of 396 patients who had propensity score matching for host, anaesthetic and operative factors, 204 matched patients were identified. The addition of oral antibiotics and MBP was associated with a significantly reduced postoperative inflammatory response (reduced postoperative Glasgow Prognostic Score) on day 3 (odds ratio (OR) 0·66, 95 per cent c.i. 0·44 to 0·99; P = 0·013) and day 4 (OR 0·46, 0·30 to 0·71; P = 0·001). Significantly reduced overall complications (OR 0·31, 0·17 to 0·56; P < 0·001), infective complications (OR 0·41, 0·22 to 0·77; P = 0·011), surgical-site infection (OR 0·37, 0·17 to 0·83; P = 0·024) and postoperative length of hospital stay (median 7 days versus 8 days in patients who had intravenous antibiotics alone; P = 0·050) were also observed.

Preoperative oral antibiotics and MBP in addition to prophylactic intravenous antibiotics were associated with a reduction in the postoperative systemic inflammatory response and postoperative complications in patients undergoing resectional left-sided colonic or rectal surgery.