**1.1 MBP alone**

Before elective colorectal surgery, MBP was a standard method of care for over a century. The earliest mention in the literature about the practice of bowel decontamination was published in British Medical Journal in November 1899 by Burney Yeo in his article "a discussion of intestinal antiseptics" [30]. It has been performed since 1930 without any clear evidence of a reduction in complication [31]. There is a long history of research on preoperative MBP in colorectal surgery [32]. The most debated aspect of bowel preparation is its role in reducing surgical morbidity, such as surgical site infection (SSI) [29]. The SSI rate is highest in colorectal surgery, which

#### *Bowel Preparation before Elective Colorectal Surgery: Its Current Role DOI: http://dx.doi.org/10.5772/intechopen.107093*

varies between 5.4% and 23.2%, with a mean of 11.4% [33]. However, the evidence does not show any benefit of MBP in reducing the mucosa-associated bacterial load in the colon. Preoperative preparation before elective colorectal surgery was shifted to outpatient care, and the mortality rate continued to decrease. Surgeons started questioning the need for the MBP, and many centers appeared to confirm the abandonment of MBP [34]. One multicenter randomized control trial (RCT) published by Contant et al. with 1345 patients did not demonstrate any significant difference in anastomotic leak rates between patients who received MBP (n = 670) and those who did not (n = 684) [35]. In 2007, Jung et al. published another retrospective study of 1343 cases that reported similar results and suggested the omission of MBP before colorectal surgery [36]. Bucher et al. demonstrated significant adverse effects associated with MBP, such as loss of superficial mucus and infiltration of polymorphonuclear cells and lymphocytes suggesting inflammatory changes in the mucosa [37]. Several case reports demonstrated adverse side effects of MBP such as seizures and electrolyte imbalance such as hyponatremia, hypernatremia, hypocalcemia, and hyperphosphatemia [38–41]. The available agents for MBP are polyethylene glycol (PEG), sodium phosphate (NaP), and picosulphate. They have unpleasant side effects as well as the process is time-consuming. The preparation of sodium phosphate is palatable and made in 300 ml of water [42]. It principally acts as a purgative. Although it is better tolerated by the patients but is associated with fluid and electrolyte imbalance. It should not be given in patients with congestive cardiac failure, cirrhosis, or chronic kidney disease [43]. Full MBP in most RCT is done with an osmotic agent such as PEG with an electrolyte solution. The PEG–electrolyte solution is prepared in 2 liters (L) of water. The patient drinks 2 L of PEG–electrolyte solution and 1 L of clear fluid. PEG electrolyte solution minimizes fluid and electrolyte imbalance [44]. The outcome of agents such as sodium phosphate (NaP) or picosulphate in bowel preparation has not been studied as much as has been done with PEG. A clinical trial by Itani et al. in 2007 compared PEG with sodium phosphate and concluded that sodium phosphate is superior to PEG in bowel preparation [45]. Sodium phosphate (NaP) can be used as an enema or an oral preparation, but PEG is used as oral preparation only. The unclear benefit of MBP is a reduction in bacterial load within the bowel as it removes solid fecal content, makes easier manipulation of the bowel during surgery, and helps in performing intraoperative colonoscopy if needed. A number of RCTs [15, 16, 46–54], meta-analyses [55–63], and one Cochrane review [63] on MBP have been published but none of these have conclusively recommended any significant benefit of MBP alone in elective colorectal surgery. MBP has possible disadvantages, such as patient discomfort in the form of nausea, vomiting, abdominal distension, insomnia, and weakness. Other significant complications include fluid and electrolyte imbalance and alteration of gut microbiota and colonic mucus layer, which has been shown to cause increased bacterial translocation [37, 64]. However, the addition of nonabsorbable oral antibiotics with MBP decreases the SSI rates by approximately 40% when compared with that of MBP alone [25, 65, 66]. Many research studies have also evaluated bowel preparation with rectal enema alone without MBP and POA, and have observed a similar rate of wound infection and anastomotic dehiscence. However, bowel preparation with rectal enema alone without MBP and POA is not recommended (weak recommendation based on moderate-quality evidence, 2B) [67]. Preoperative MBP alone, without POA, is also not recommended for patients undergoing elective colorectal surgery (Grade of recommendation: strong recommendation based on high-quality evidence, 1A) [68].

#### **1.2 MBP plus preoperative prophylactic oral antibiotics**

Another aspect of bowel preparation is adding preoperative prophylactic oral antibiotics (POA) with MBP. Bowel preparation before colorectal surgery with POA was first proposed by Poth et al. in 1942 [69]. Whereas the combination of POA with MBP before elective colorectal surgery was introduced by Nichols et al. in 1971 [70]. In their landmark prospective randomized control trial comparing MBP with or without preoperative nonabsorbable oral antibiotics, Nichols et al. concluded a marked decrease in SSI with the use of a combination of MBP and POA [8, 70]. In their RCT, they used neomycin and erythromycin base and MBP. Interestingly, other studies have failed to demonstrate any significant protective benefit of this regimen against postoperative complications. Nichols et al., from their study, concluded that MBP did not decrease the microbial burden; rather, it facilitated the effect of oral antibiotics to decrease the mucosal concentration of bacteria [8, 70]. In 1980, most American and Canadian surgeons started using oral and parenteral antibiotic prophylaxis and MBP [71]. Later Smith MB et al., in 1990, highlighted the importance of oral antibiotics over intravenous antibiotics [72]. In 2002, Lewis conducted a prospective trial comparing parenteral antibiotics alone with a combination of parenteral and oral antibiotics. However, MBP was done in both these groups. He reported a lower incidence of SSI in the oral and parenteral antibiotic group [73]. In 2010, Markell et al., in their study, showed that only 39% of surgeons are using a POA, which was a substantial decrease in oral antibiotics use when compared to 1990 [74]. In the year 2015, combination of POA with MBP in elective colorectal surgery was reintroduced, but it became widespread in 2016 [75]. It is presumed that a combination of these two will give a synergistic effect. Nonabsorbable oral antibiotics, when combined with MBP, further reduce the intraluminal bacterial load and SSI rates [76]. However, the choice of antibiotics for this purpose is not clear. Different clinical trials have used different antibiotics, but these did not conclude which is better. Our knowledge has not moved beyond the existing formulation regimens for bowel preparation to advance our understanding of the pathogenesis of SSI and anastomotic leak. Overall perception indicates that antibiotics with both aerobic and anaerobic cover should be chosen [77]. Unfortunately, antibiotics used for bowel preparation have not changed in decades despite recognizing antibiotic resistance in surgical patients [78, 79]. Kirby et al., in their article, described the need for recalibration of antibiotics after reports from Leeds, United Kingdom, suggesting resistant Enterobacteriaceae responsible for SSI [80]. A randomized control trial by Clarke et al. demonstrated the role and efficacy of oral antibiotics in reducing SSI in elective colorectal surgery [81]. Many studies to date have demonstrated that oral nonabsorbable antibiotics before elective colorectal surgery prevent anastomotic leak more effectively than intravenous antibiotics alone [32]. The most common prophylactic oral antibiotic regimen used in these studies for preoperative bowel preparation is Neomycin (1 g) and Metronidazole (1 g) two times a day before surgery. However, the microbiological basis of this is unverified [82]. Only a few randomized clinical trials are in the literature on POA alone without MBP and POA with MBP. A recent meta-analysis conducted in 2018, which included two RCTs (n = 709) and two cohort studies (n = 22,774), did not find any difference in the overall incidence of SSI between the groups or even when RCTs and cohort studies were analyzed separately [83]. However, there is little level 1 evidence for POA alone without MBP [13], and therefore, preoperative POA without MBP is not recommended (Grade of recommendation: weak recommendation based on low-quality evidence, 2C) [29]. There is also no consensus on the optimal type of

#### *Bowel Preparation before Elective Colorectal Surgery: Its Current Role DOI: http://dx.doi.org/10.5772/intechopen.107093*

bowel preparation. Nichols et al. used the combination of oral Neomycin (1 g) and Erythromycin (1 g) dosages at 1:00 pm, 2:00 pm, and at 11:00 pm (total 6 g) a day before surgery along with MBP. They could reduce the fecal aerobic and anaerobic flora [84]. Neomycin and Erythromycin combination has been used for decades without any evidence of major side effects and many centers use a full MBP using PEG with electrolyte solution and two doses of oral Neomycin (1 g) and Metronidazole (1 g). Kim et al., in 2014, compared MBP with or without POA and found a significantly lower risk of surgical site infection (SSI) and Clostridium difficile colitis when both were used in combination. Michigan Surgical Quality Collaboration (MSQC) recommends full MBP and POA before colorectal surgery unless there is a contraindication for the same [85]. In 2015, Scarborough et al. compared the POA alone versus POA combined MBP, and their result supports the routine utilization of MBP with POA [17]. However, their POA alone group was comparatively smaller in size than the combined MBP and POA [17]. ERAS society also recommends the combination of preoperative MBP and POA before elective colorectal surgery [28]. Many centers use POA alone before elective colorectal surgery. Their results of using POA have been assessed in two large retrospective studies conducted by the American College of Surgeons National Surgical Quality Improvement Program (NSQIP) on more than 30,000 patients and one large prospective meta-analyses on 69,000 patients. These have shown almost comparable or lower SSI rates among patients who received MBP plus POA versus those who received MBP alone [27, 83, 86]. Preoperative MBP and preoperative POA in elective colorectal surgery are recommended (strong moderatequality evidence, 1B) [75, 87–90]. Currently, the practice can be summed up as: the MBP can be started two days before surgery and must be completed one day before surgery by 15:00 hours. The patient takes 1 g of Neomycin and 1 g of Metronidazole orally after completion of MBP at 15:00 and 23:00 hours. One hour before surgery, the patient should also receive perioperative intravenous antibiotics (Cefuroxime 1.5 g and Metronidazole 500 mg). The dose of intravenous antibiotics can be repeated if the duration of surgery is more than 3 hours [44].
