Risk Factors Analysis for Surgical Site Infection Following Elective Colorectal Resection: A Retrospective Regression Analysis
Surgical site infections (SSIs) are a significant post-operative complication following elective colorectal surgery, often leading to prolonged hospital stays, increased healthcare costs, and higher mortality rates. Despite their impact, few studies have comprehensively evaluated the risk factors associated with SSIs. This study aims to fill this gap by analyzing the relative correlation of medical, environmental, and patient-related factors contributing to the incidence of all types of SSIs.
The study conducted a retrospective search of the patient database at the Gastrointestinal Surgery Center of the Third Affiliated Hospital of Sun Yat-sen University from January 2011 to August 2017. The data included pre-operative demographic and surgical information, which were recoded according to the study protocol. Univariate and multivariate analyses were performed to identify factors affecting SSI incidence. Additionally, propensity analysis was conducted to minimize bias in demographic characteristics and explore the prophylactic effect of pre-operative oral antibiotics.
The univariate analysis revealed that younger age (odds ratio [OR]: 0.378; 95% confidence interval [CI]: 0.218–0.657) and pre-operative oral antibiotic use (OR: 0.465; 95% CI: 0.255–0.850) were protective factors against SSIs. Conversely, pre-operative anemia (OR: 4.591; 95% CI: 2.567–8.211), a history of neoadjuvant chemotherapy (OR: 2.398; 95% CI: 1.094–5.256), and longer surgical duration (OR: 2.393; 95% CI: 1.349–4.246) were identified as risk factors. The multivariate analysis confirmed that age (P = 0.003), surgical duration (P = 0.001), and pre-operative oral antibiotic use (P < 0.001) were independent factors influencing SSI incidence. Propensity-matched analysis further supported the protective effect of oral antibiotics, showing that a 1-day course was as effective as a 3-day course.
The study enrolled 581 patients who underwent elective colorectal surgeries, with 57 developing SSIs, resulting in an overall incidence rate of 9.81%. The types of SSIs included superficial incisional SSI (SSSI), deep incisional SSI (DSSI), and organ space infection (OSI). The mean post-operative length of stay (LOS) in the SSI group was significantly longer (16.1 ± 9.3 days) compared to the non-SSI group (8.9 ± 3.8 days). Additionally, the total hospitalization expense was higher in the SSI group (81,704.26 ± 46,920.38 RMB) than in the non-SSI group (60,404.29 ± 16,815.52 RMB).
The univariate analysis of baseline characteristics indicated that age less than 65 years was a protective factor (OR: 0.378; 95% CI: 0.218–0.657), while pre-operative anemia (OR: 4.591; 95% CI: 2.567–8.211) and neoadjuvant chemotherapy (OR: 2.398; 95% CI: 1.094–5.256) were risk factors. Gender, smoking status, BMI, diabetes, hypertension, and low albumin levels did not show significant associations with SSI incidence.
For surgical and pathological factors, the univariate analysis identified that the combination of pre-operative oral antibiotics and mechanical bowel preparation (MBP) (OR: 0.465; 95% CI: 0.255–0.850) and surgical duration longer than four hours (OR: 2.393; 95% CI: 1.349–4.246) were associated with SSI incidence. The surgical approach, surgical region, pathological stage, and individual TNM stage did not show significant associations.
The multivariate analysis confirmed that surgical duration longer than four hours was associated with an increased SSI risk (P = 0.003), while age less than 65 years (P < 0.001) and the combination of oral antibiotics and MBP (P = 0.001) reduced SSI incidence. A Hosmer-Lemeshow test confirmed the efficiency of the logistic regression model (P = 0.285), indicating no evidence of a poor fit.
Stratification analysis of patients with SSSI or OSI showed that surgical duration longer than four hours (P = 0.002) was associated with an increased risk of SSSI, while age less than 65 years (P = 0.004) and oral antibiotic use (P = 0.021) were protective factors for SSSI. For OSI, age less than 65 years (P = 0.044) was the only protective factor identified.
To further explore the prophylactic effect of pre-operative oral antibiotics, a propensity-matched analysis was conducted. Patients were matched based on age, sex, BMI, tumor stage, neoadjuvant chemotherapy history, ASA grade, smoking status, surgical site, surgical approach, and surgical duration. The analysis confirmed the protective effect of oral antibiotics combined with MBP (OR: 0.024; 95% CI: 0.009–0.096). Additionally, a 1-day course of antibiotics was found to have a similar protective effect as a 3-day course.
The study highlights the importance of pre-operative oral antibiotic use in reducing SSI incidence following elective colorectal surgery. While age and surgical duration are significant factors, they are either demographic or unpredictable. In contrast, pre-operative oral antibiotic use is a controllable factor that can significantly reduce SSI risk. The findings suggest that a 1-day course of oral antibiotics is sufficient to provide the protective effect, thereby minimizing potential drug-related morbidities and financial burdens on patients.
In conclusion, this study identifies age less than 65 years, surgical duration longer than four hours, and pre-operative oral antibiotic use as independent factors influencing SSI incidence. Among these, pre-operative oral antibiotic use combined with MBP is the only actionable method recommended for reducing SSI risk. A 1-day course of oral antibiotics is sufficient to achieve this protective effect, making it a practical and effective strategy for improving post-operative outcomes in elective colorectal surgery.
doi.org/10.1097/CM9.0000000000000670
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