Diagnoses influence surgical site infections (SSI) in colorectal surgery: a must consideration for SSI reporting programs?

Background: Colorectal surgery is associated with high rates of surgical site infection (SSI). The National Surgery Quality Improvement Program is a validated, risk-adjusted quality-improvement program for surgical patients. Patient stratification and risk adjustment are associated with Current Procedural Terminology codes and primary disease diagnosis is not considered. Our aim was to determine the association between disease diagnosis and SSI rates.

Methods: Data from all 2009 National Surgery Quality Improvement Program institutions were analyzed. ICD-9 codes were used to differentiate patients into cancer (colon or rectal), ulcerative colitis, regional enteritis, diverticular disease, and others. Diagnosis-specific SSI rates were compared with benign neoplasm, which had the lowest rate (8.9%). Logistic regression was performed adjusting for age, body mass index, American Society of Anesthesiologists classification, wound type, and relative value unit.

Results: There were 24,673 colorectal procedures, with 1,956 superficial incisional (SSSI), 398 deep incisional (DSSI), and 1,096 organ/space (O/SSSI) infections. Odds ratio (OR) and 95% confidence intervals compared with benign neoplasm diagnosis were computed after adjustment for each diagnosis category. In rectal cancer patients, significantly more SSSI (OR = 1.6; 95% CI, 1.3-2.1; p < 0.0001), DSSI (OR = 2.1; 95% CI, 1.3-3.7; p = 0.006), and O/SSSI (OR = 2.2; 95% CI, 1.6-3.0; p < 0.0001) developed. In diverticular patients, more SSSI (OR = 1.6; 95% CI, 1.3-2.0; p < 0.0001), but not DSSI or O/SSSI, developed. In ulcerative colitis patients, more DSSI (OR = 2.4; 95% CI, 1.2-4.9; p = 0.01), O/SSSI (OR = 2.1; 95% CI, 1.4-3.1; p = 0.0004), but fewer SSSIs, developed.

Conclusions: We found that SSI type is associated with the underlying disease diagnosis. To facilitate colorectal SSI-reduction efforts, the disease process must be considered to design appropriate interventions. In addition, institutional comparisons based on aggregate or stratified SSI rates can be misleading if the colorectal disease mix is not considered.