We analyzed the efficacy and safety of aminoglycosides in a retrospective study of 415 patients with acute appendicitis and 277 patients with acute cholecystitis. The following variables increased the incidence of postoperative complications, defined as surgical site infection, recurrent intraabdominal infection, non-infectious post-operative complication, or death: age (p = 0.016 and 0.011), kidney disease (p = 0.019 and <0.001), and ASA Score (p < 0.001). The type of antibiotic therapy did not have a statistically significant effect on the incidence of postoperative complications in patients with acute appendicitis and cholecystitis (p = 0.561 and 0.547, respectively). A linear regression model showed a higher complication rate in patients with kidney disease (p = 0.014) and neoplasms (p = 0.013); the type of antibiotic therapy did not have a significant effect on the outcome (p = 0.765). There was no statistically significant difference in the post-treatment levels of creatinine in patients treated with aminoglycosides (gentamicin 3 mg/kg once daily) and in those who received other antibiotics (p = 0.75).