Oral antibiotics and mechanical bowel preps: do they have to come together?

Dear Editor:

Rybakov et al. have published an RCT of oral (O) and IV versus IV alone antibiotic prophylaxis in rectal surgery, excluding the colon [1]. They found very similar results to the 36 studies which compared IV to O plus IV in a systematic review (SR) of 61 RCTs including 12,971 colorectal surgery patients, looking at this question from several angles [2]. All 37 of these studies used a mechanical bowel prep (MBP) whenever O was used (and not with IV alone) and also in the 19 studies of O vs. IV plus O alone in that same SR. The combined risk ratio was almost the same going both ways (0.47 vs 0.48). Rybakov pointed out that studies have been done showing MBP alone does nothing to diminish SSI (surgical wound infection). But what if MBP really did nothing? The error in all these studies is that there were two variables that separated the experimental and control groups—antibiotic entry and MBP. There must be only one. In fact the studies to explore MBP alone were also included in the SR: IV + O, +/− MBP in five studies which showed a slight benefit for no MBP, and two studies of IV + O compared to IV alone with no MBP in either group. This showed the same benefit of two antibiotics as the studies above. More studies of this last structure are needed to put this issue to bed. Our patients will appreciate that.


  1. 1.

    Rybakov E, Nagudov M, Sukhina M, Shelygin Y (2021 Feb) Impact of oral antibiotic prophylaxis on surgical site infection after rectal surgery: results of randomized trial. Int J Colorectal Dis. 36(2):323–330. https://doi.org/10.1007/s00384-020-03746-0

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  2. 2.

    Nelson RL, Hassan M, Grant MD (2020 Dec) Antibiotic prophylaxis in colorectal surgery: are oral, intravenous or both best and is mechanical bowel preparation necessary? Tech Coloproctol. 24(12):1233–1246. https://doi.org/10.1007/s10151-020-02301-x

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Correspondence to Richard Nelson.

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Nelson, R. Oral antibiotics and mechanical bowel preps: do they have to come together?. Int J Colorectal Dis (2021). https://doi.org/10.1007/s00384-021-03882-1

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