Differing Risk Factors for Incisional and Organ/Space Surgical Site Infections Following Abdominal Colorectal Surgery

OBJECTIVE: Surgical site infections are a major source of morbidity after colorectal surgery. The aim of this study was to explore differences between incisional and organ/space surgical site infection types by evaluating risk factors, National Nosocomial Risk Index Scores, and clinical outcomes. DESIGN: A random sample of adults undergoing abdominal colorectal surgery between June 2001 and July 2008 was extracted from a colorectal surgery practice database. Patient factors, comorbidities, intraoperative factors, postoperative factors, and infection were collected; risk score (from - 1 to 3 points) was calculated. Variables associated with surgical site infection by univariate analysis were incorporated in a multivariable model to identify risk factors by infection type. Infection risk by risk score was evaluated by logistic regression. Length of stay, readmission, and mortality were examined by infection type. RESULTS: Six hundred fifty subjects were identified: 312 were male, age was 59.8 (SD 17.8) years. Common preoperative diagnoses included colorectal cancer (36.9%) and inflammatory bowel disease (21.7%). Forty-five cases were emergencies, and 171 included rectal resections. Eighty-two patients developed incisional and 64 developed organ/space surgical site infections. Body mass index was associated with incisional infection (OR 1.05, 95% CI 1.00-1.09), whereas previous radiation (OR 4.49, 95% CI 1.53-13.18), postoperative hyperglycemia (OR 2.99, 95% CI 1.41-6.34), preoperative [albumin] (OR 0.52, 95% CI 0.36-0.76), and case length (OR 1.26, 95% CI 1.08-1.47) were associated with organ/space infection. A risk score of 2 and above, compared with a score of <2, predicted organ/space (OR 5.92, 95% CI 3.16-11.09) but not incisional infection (OR 0.95, 95% CI 0.41-2.16). Organ/space infections were associated with longer length of stay (P = .006) and higher readmission rates (P < .001) than incisional infections. CONCLUSIONS: Risk factors for surgical site infections differ by type of infection. Clinical outcomes and value of the risk index score are different by infection type. It may be prudent to consider incisional and organ/space surgical site infections as different entities for patients undergoing colorectal surgery.