Epidemiology and Risk Factors for Superficial Surgical Site Infections after Appendectomy for Acute Appendicitis: A Secondary Data Analysis.

Background: The identification of risk factors for superficial surgical site infections (SSSIs) associated with appendectomy is paramount in the management of patients with acute appendicitis (AA). Methods: This study was a secondary data analysis from a prospective multi-center observational study. It included all consecutive hospitalized patients with AA who underwent appendectomy and were monitored for complications at 30 days after the intervention. A case-control approach was used to evaluate risk factors associated with the occurrence of SSSI. Results: Among 2,667 patients, 156 (5.8%) developed an SSSI. The series included 1,449 males (54.3%) and 1,218 females with a median age of 29 years (interquartile range [IQR] 20-45 years). Antimicrobial therapy within the previous 30 days was reported by 170 patients (6.4%), and a C-reactive protein concentration (CRP) >50 mg/L was observed in 609 (22.8%). A total of 960 patients (36.0%) underwent open surgery, 1,699 (63.7%) laparoscopic surgery, and 8 (0.3%) another surgical intervention. In 2,575 patients (95.6%), a pathological appendix was detected during the operation. In 776 patients (29.1%), an intra-operative abdominal drain (IAD) was placed; 125 patients (4.7%) were admitted to the intensive care unit. The median hospital length of stay was 3 days (IQR 2-5 days). The overall mortality rate was 0.11%. Multinomial logistic regression analysis of risk factors demonstrated that statistically significant risk factors independently associated with the occurrence of SSSIs were antimicrobial therapy within the previous 30 days, CRP >50 mg/L, open surgical procedures, presence of IAD, and intra-operative findings of complex appendicitis. Conclusions: Knowledge of five easily recognizable variables, assessable at hospital admission or as soon as the surgical intervention is concluded, might identify patients with a greater risk of developing an SSSI.