Contant et al. studied 1431 patients undergoing open colorectal resection randomized to intravenous antibiotics (aerobic and anaerobic coverage) with or without MBP [9]. The data demonstrated a significant increase in the rate of intra-abdominal abscess without MBP (2.5 % vs 0.3 %), however there was no significant difference in superficial wound infection (no-MBP-14 % vs MBP- 13.8 %) or anastomotic leak (no-MBP-5.4 % vs MBP-4.8 %). The authors concluded that mechanical bowel preparation can be safely avoided. Jungl et al. performed a similarly designed study of 1505 open colectomy patients and also concluded that there was no significant difference in wound infection (MBP- 7.8 % vs N-MBP- 6.4 %) or anastomotic leak (MBP-2 % vs no-MBP 2.6 %) [10]. The recent meta-analysis by Bucher et al. included 7 RCTs available in the literature. This meta-analysis revealed a higher incidence of anastomotic dehiscence in patients receiving MBP, 5.6 % (36/642), vs no MBP 2.8 % (18/655) (P = .03; OR, 1.85 [95 % CI, 1.06–3.22]) [11]. However, using a number need to treat analysis (NNT) and an incidence of 5 % for anastomotic leaks, 32 patients (95 % CI, 19–306) would have to be operated on without MBP to prevent one leak in a patient receiving MBP before surgery. The rate of intra-abdominal infection (peritonitis or abscess) was similar in the MBP group, 3.7 % (17/458), compared with the no-MBP group, 2.0 % (9/461) (OR, 1.69 [95 % CI, 0.76–3.75]; P = .18). The rate of wound infection was slightly higher in patients receiving MBP, 7.5 % (48/642), vs no MBP, 5.5 % (36/655) (OR, 1.38 [95 % CI, 0.89–2.15]; P = .15). General complication and extra-abdominal morbidity rates were not significantly different in any of these studies; this finding was confirmed in the meta-analysis. Because of the significant impact of anastomotic leaks, the Bucher meta-analysis would favor the avoidance of MBP in terms of mortality rates (OR, 1.42 [95 % CI, 0.37–5.45]; P = .60). The systematic review performed by Wille-Jorgenson arrived at the same conclusion [12].

A major limitation of the “no bowel prep” philosophy was the failure to understand that these data were obtained in the absence of the documented superior treatment arm, mechanical bowel prep with oral antibiotics. Therefore, the more accurate conclusion from these data is that bowel prep without oral antibiotics is equivalent to no mechanical bowel prep. The recent report from the Michigan Surgical Quality Consortium which analyzed 2062 elective colectomies between January 2008 and June 2009 compared 49.6 % of patients with mechanical prep only to 36.4 % with mechanical prep and oral antibiotics [13]. Patients receiving oral antibiotics were less likely to have any SSI (4.5 % vs. 11.8 %, p = 0.0001), to have an organ space infection (1.8 % vs. 4.2 %, p = 0.044) and to have a superficial SSI (2.6 % vs. 7.6 %, p = 0.001). Interestingly, patients receiving bowel prep with oral antibiotics were also less likely to have a prolonged ileus (3.9 % vs. 8.6 %, p = 0.011). Fry recently reviewed the published literature and found MBP alone did not reduce SSIs in nine prospective randomized trials between 2000 and 2010 [14]. He then performed a meta-analysis of nine randomized clinical trials of MBP which showed the superiority of oral and intravenous antibiotics versus only intravenous antibiotics [odds ratio 0.47 (95 % CI: 0.16–0.77, p < 0.0001)]. Furthermore the rate of SSIs decreased by 6.18 % (95 % CI: 3.43–8.94) with MBP using oral and intravenous antibiotics [14].

More recently, there has been a concerted effort to revisit the impact of bowel prep with antibiotics as part of quality improvement projects. Althumari performed an analysis of the American College of Surgeons National Surgical Quality Improvement Program Colectomy Targeted Participant Use Data File for 2012 and 2013 [15]. The analysis of 19,686 patients (25.7 % no bowel prep; 40.7 % received MBP only; 3.3 % oral antibiotics only; 30.3 % received MBP plus oral antibiotics). Patients who received MBP plus oral antibiotics had a lower incidence of superficial SSI, deep SSI, organ space SSI, any SSI, anastomotic leak, postoperative ileus, sepsis, readmission and reoperation compared with patients who received neither (all P < 0.01). The reduction in SSI incidence was associated with a reduction in wound dehiscence, anastomotic leak, pneumonia, prolonged requirement of mechanical ventilator, sepsis, septic shock, readmission, and reoperation. Kiran analyzed a portion of the same National Surgical Quality Improvement Program-targeted colectomy data and also concluded that mechanical bowel prep with oral antibiotics reduced the rates of SSI, anastomotic leak, and ileus by nearly half [16].

Wick et al. evaluated the impact of the implementation of a pathway designed to improve patient outcomes which adopted a mechanical bowel preparation with oral antibiotics at their institution. Compared to a historical control group, there was a significant reduction in SSI (18.8 % vs 7.3 %). Collins et al. analyzed long term data from a 1999 to 2005 randomized study comparing mechanical bowel preparation (no oral antibiotics) to no prep and demonstrated that prep was associated with significantly fewer recurrences, and better cancer-specific and overall survival in the MBP group after 10 years [17]. Finally, a more recent meta-analysis assessing seven randomized controlled trials that consisted of 1769 cases determined that both total surgical site infection and incisional surgical site infection were significantly reduced in patients who received oral and systemic antibiotics with a mechanical bowel preparation (total: 7.2 % vs 16.0 %, p < 0.00001; incisional: 4.6 % vs 12.1 %, p < 0.00001) [18]. Therefore, the current body of data would support the re-introduction (or continued practice) of the combination of mechanical bowel prep with oral antibiotics as well as prophylactic intravenous antibiotics for optimal outcomes including surgical site infection and the related secondary complications in colectomy patients.