Retrospective Analysis of Post-Operative Antibiotics in Complicated Appendicitis

Background: There is no consensus regarding the ideal post-operative antibiotic strategy for surgically managed complicated appendicitis. The goal of this study was to investigate different antibiotic regimens used for this purpose at our institution and their association with post-operative outcomes. Methods: The 1,102 patients underwent appendectomy from 2012 to 2016. A detailed chart review was performed on the 188 with complicated appendicitis based on standardized definitions. Descriptive and inferential statistics were used to analyze post-operative antibiotic use and complications. Results: Of the 188 cases of complicated appendicitis, 143 (76%) were classified as perforated by the operative surgeon. These patients were significantly more likely to be started on antibiotics after appendectomy (83.9% versus 33.3%; p < 0.001) and have a greater length of stay (LOS) (p = 0.006). The development of a surgical site infection (SSI) was significantly associated with a clinical diagnosis of diabetes (p = 0.04); the presence of free fluid, abscess, or perforation on pre-operative imaging (p = 0.002, 0.039, and 0.012, respectively); and a decision by the surgeon to leave a drain (p = 0.001). On multiple logistic regression analysis adjusted for free fluid on pre-operative imaging and an intra-operative decision to leave a drain, patients receiving one day or three or more days of antibiotics had higher odds of developing an SSI than patients who did not receive any post-operative antibiotics. Conclusions: In this cohort, operative surgeons accurately identified patients with complicated appendicitis who did not require post-operative antibiotics. For patients deemed to require them, two days of treatment was associated with reduced odds of SSI compared with shorter or longer antibiotic courses. The optimal course of antibiotics remains to be identified, but these findings suggest that longer post-operative courses do not avert SSI compared with two days of antibiotics. A prospective trial could clarify the optimal duration and route of antibiotic therapy in the setting of surgical complicated appendicitis.