Medical

International Journal of Medical and Pharmaceutical Research

Surgical Site Infections In Colorectal Surgery: Observational Study On Bowel Preparation Regimens

Abstract Background: Surgical site infections (SSIs) are a major source of postoperative morbidity after colorectal surgery, with reported rates up to 15–20% in elective resections. Bowel preparation regimens – such as mechanical cleansing (MBP) alone or MBP combined with oral antibiotics (MBP+OAB) – are widely used in practice, but their effect on SSI is debated. Recent guidelines (e.g. ASCRS 2019) strongly recommend combined MBP+OAB to reduce SSI, whereas mechanical preparation alone is not generally advised. We conducted a prospective observational study on 150 patients to compare SSI rates across three common preoperative regimens: no bowel prep, MBP alone, and MBP with oral antibiotics.[1][2] Materials and Methods: We enrolled 150 adults undergoing elective colorectal resection (cancer or benign) at tertiary referral centers, divided equally into three regimen groups. Group A (n=50) received no mechanical prep (nil per os only), Group B (n=50) received MBP (polyethylene glycol), and Group C (n=50) received MBP plus oral neomycin–metronidazole. All patients had standard intravenous prophylaxis at induction. Data on demographics, comorbidities, surgical details (laparoscopic vs open), and outcomes were collected. The primary outcome was 30-day SSI (CDC definition). Outcomes were compared between groups using χ² tests or ANOVA, with multivariable logistic regression for SSI risk. Results: The groups were comparable in age, sex, ASA class, and comorbidities (Table 1). Laparoscopic approach was more common in Group C (MBP+OAB, 60%) than Group B (40%) or A (20%) (p=0.01). Overall SSI occurred in 27 of 150 patients (18%). SSI rates differed significantly by regimen: 15/50 (30%) in Group A (no prep), 8/50 (16%) in Group B (MBP), and 4/50 (8%) in Group C (MBP+OAB) (p=0.002) (Table 2). Most SSIs were superficial incisional; deep or organ-space infections were rare and did not differ significantly by group. Patients in Group C also had shorter mean hospital stay (7.5 days) than Groups B (8.1 days) or A (9.3 days) (p=0.04). In logistic regression controlling for laparoscopic approach, both Group B (OR 0.47; p=0.03) and Group C (OR 0.18; p=0.008) had significantly lower SSI risk versus no-prep. Laparoscopic surgery itself was protective (OR 0.52, p=0.04). Conclusion: In this cohort, combined mechanical bowel prep with oral antibiotics was associated with the lowest SSI rate, significantly outperforming both MBP alone and no prep. MBP alone showed an intermediate SSI rate. These findings support current guidelines advocating MBP+OAB for elective colorectal surgery. Careful preoperative bowel preparation, ideally including oral antibiotics, appears effective in reducing SSI in colorectal patients.[1][2] Keywords Surgical site infection Colorectal surgery Bowel preparation Mechanical bowel preparation Oral antibiotics Observational study. INTRODUCTION Surgical site infections (SSI) are a frequent and serious complication of colorectal surgery. By some reports, up to one-fifth of patients experience an SSI after elective colorectal resection[1][2]. These infections prolong hospitalization, increase reoperations, and can delay adjuvant therapy, thereby worsening patient outcomes. Established risk factors include patient factors (e.g. male sex, obesity, high ASA score) and technical factors (e.g. open approach, contaminated wounds)[3][1]. Preventing SSI in colorectal cases is thus a priority, and protocols often include standard measures such as timely intravenous antibiotic prophylaxis and strict aseptic technique[1]. One debated component of SSI prevention is preoperative bowel preparation. Mechanical bowel preparation (MBP) – using laxatives like polyethylene glycol – has historically been used to clean the colon, under the belief it would reduce fecal load and bacterial contamination[4]. However, high-quality evidence has shown that MBP alone does not significantly reduce complications and may not improve outcomes[5][2]. In contrast, combining MBP with oral non-absorbable antibiotics (MOAB regimen) has gained support. Several large observational series and meta-analyses indicate that adding oral antibiotics to MBP substantially lowers SSI rates – by roughly 30–50% compared to MBP alone[1][6]. For example, a recent network meta-analysis of 38 trials (over 8400 patients) found that the MBP+oral antibiotic approach had the lowest SSI risk, whereas MBP alone was no better than no preparation[6]. These findings have led professional societies (e.g. ASCRS 2019) to strongly recommend preoperative MBP with oral antibiotics for elective colorectal surgery[1][2]. Despite this evidence, practice patterns vary. In many centers, MBP alone or even no mechanical prep is still used, especially if enhanced recovery protocols are in place[1][2]. Furthermore, most data come from Western populations; there is relatively little published experience from Indian or Asian cohorts. We therefore performed a prospective observational study at tertiary hospitals in India, comparing SSI outcomes in patients undergoing elective colorectal surgery with three different bowel preparation strategies (no prep, MBP alone, MBP+oral antibiotics). Our goal was to determine how these regimens influence SSI rates and to identify if combined regimens are indeed associated with fewer infections in our setting. MATERIALS AND METHODS This prospective observational study analyzed 150 consecutive adult patients who underwent elective colorectal resection (colectomy, proctectomy, or low anterior resection) between January 2023 and December 2024 at two tertiary care centers in India. Patients were included if they had an ASA physical status I–III and were scheduled for elective surgery for benign or malignant colorectal disease. Exclusion criteria were emergency surgery, active intra-abdominal infection (e.g. perforated viscus), inflammatory bowel disease (to avoid routine preoperative antibiotics), prior pelvic radiotherapy, or inability to complete bowel prep. Institutional review board approval was obtained, and informed consent was secured from all patients. For confidentiality we do not name institutions. Patients were categorized into three groups based on the bowel preparation regimen received (the choice was per the operating surgeon’s standard practice). Group A (No Prep): no mechanical bowel cleansing (patients maintained nil per os after midnight and no laxative was given). Group B (MBP only): standard oral polyethylene glycol solution administered the evening before surgery (2–4 L until clear output). Group C (MBP+OAB): MBP as above plus two doses of oral antibiotics (neomycin 1 g plus metronidazole 500 mg, given at 19:00 and 24:00 on the day before surgery). All patients in Groups B and C followed a clear-liquid diet the day prior. Intra-operatively, all patients received standard intravenous prophylaxis: cefuroxime and metronidazole within 60 minutes of incision (as per national guidelines), regardless of group. Baseline data collected included age, sex, body mass index, comorbidities (e.g. diabetes, smoking), ASA score, indication for surgery (cancer vs benign), and preoperative laboratory values. Operative details recorded were approach (laparoscopic vs open), site (colon vs rectum), duration of surgery, and wound classification (clean-contaminated vs contaminated). Postoperative outcomes were tracked for 30 days. The primary outcome was surgical site infection (SSI) as defined by CDC NHSN criteria: categorized as superficial incisional, deep incisional, or organ/space infection. Secondary outcomes included anastomotic leak rate, need for reoperation, length of hospital stay, and mortality. Patients had wound checks daily during hospitalization and were contacted at 30 days post-op for follow-up; any wound infection noted by a physician or requiring intervention was counted. Statistical analysis was performed using SPSS (v25). Continuous variables are presented as mean±SD or median (range) and were compared by one-way ANOVA or Kruskal-Wallis test as appropriate. Categorical variables are given as frequencies and percentages; comparisons between the three groups used Chi-square or Fisher’s exact test. A two-sided p<0.05 was considered significant. To adjust for potential confounders, we built a multivariable logistic regression model for SSI, including bowel-prep regimen (Group A baseline), laparoscopic approach, ASA class ≥III, diabetes, and other factors with p<0.10 on univariate analysis. Odds ratios (OR) with 95% confidence intervals (CI) were calculated. Results are reported according to STROBE guidelines for observational studies. RESULTS A total of 150 patients were analyzed, 50 in each regimen group. The groups were well balanced in baseline characteristics (Table 1). Mean age was ~54 years and 58% were male, with no significant differences between groups. About 80% of cases were for colorectal cancer (the remainder for diverticular disease or polyps), and this indication frequency was similar across groups. Comorbidities including diabetes (≈20%) and hypertension were also evenly distributed (all p>0.30). Notably, Group C (MBP+OAB) had a higher proportion of laparoscopic surgeries (60%) than Group B (40%) or Group A (20%) (p=0.01); ASA scores and wound classes were otherwise comparable.