Background: The post-operative management of simple (acute) appendicitis differs throughout the United States. Guidelines regarding post-operative antibiotic usage remain unclear, and treatment generally is dictated by surgeon preference. We hypothesize that post-operative antibiotic use for simple appendicitis is not associated with lower post-operative complication rates.

Methods: In a post-hoc analysis in a large multi-center observational study, only patients with an intra-operative diagnosis of AAST EGS Grade I were included. Subjects were classified into those receiving post-operative antibiotics (POST) and those given pre-operative antibiotics only (NONE). Clinical outcomes examined were length of stay (LOS), 30-day emergency department (ED) visits and hospital re-admissions, secondary interventions, surgical site infection (SSI), and intra-abdominal abscess (IAA).

Results: A total of 2,191 subjects were included, of whom 612 (28%) received post-operative antibiotics. Compared with the NONE group, POST patients were older (age 37 [range 26–50] versus 33 [26–46] years; p < 0.001), weighed more (82 [70–96] versus 79 [68–93] kg (p = 0.038), and had higher white blood cell counts (13.5 ± 4.2 versus 13.1 ± 4.4/10³/mcL (p = 0.046), Alvarado Scores (6 [5–7] versus 6 [5–7]; p < 0.001), and Charlson Comorbidity Indices (median score 0 in both cohorts; p < 0.001). The POST patients had a longer LOS (1 [1-2] versus 1 [1-1] days; p < 0.001). There were no differences in the number who had ED visits within 30 days (9% versus 8%; p = 0.435), hospital re-admission (4% versus 2%; p = 0.165), an index hospitalization SSI (0.2% for both cohorts; p = 0.69), an SSI within 30 days (4% versus 2%; p = 0.165), index hospitalization IAA rate (0.3% versus 0.1%; p = 0.190), 30-day IAA (2% versus 1%; p = 0.71), index hospitalization interventions (0.5% versus 0.1%; p = 0.137) or 30-day secondary interventions (2% versus 1%; p = 0.155).

Conclusions: Post-operative antibiotic use after appendectomy for simple appendicitis is not associated with better post-operative clinical outcomes at index hospitalization or at 30 days after discharge.