Predictors of Nonoperative Management Failure and Recurrence in Adults with Acute Appendicitis: A Single-Center Retrospective Study

[Purpose] Failure and recurrence are concerns in nonoperative management (NOM) for acute appendicitis (AA) and interval appendectomy (IA). The goal of the study was to identify predictors of failure and recurrence in patients with AA who underwent NOM. [Methods] A total of 348 adults with appendicitis were treated in our department from April 2016 to October 2021. Among these patients, 337 who did not undergo emergency surgery were divided into those with failed NOM and unplanned surgery (n=28) and successful NOM (n=309). These groups were compared to identify predictive factors for NOM failure. In the NOM-success group, 195 patients were divided into non-recurrence (n=166) and recurrence (n=29) groups to identify predictive factors for recurrence of appendicitis. [Results] In multivariate analysis, post-treatment CRP level (odds ratio (OR)=1.126, 95% confidence interval (CI) 1.076-1.179, P=0.000) and fecal stones with abscess formation (OR=5.530, 95% CI 2.081-14.691, P=0.001) were independently associated with NOM failure. Receiver operating characteristic curve analysis showed an optimum cutoff CRP level of 10.46 mg/dl for failure appendicitis. The initial CRP level was significantly lower and the % CRP decrease was significantly higher in the recurrence group than in the non-recurrence group. [Conclusions] These findings suggest that the post-treatment CRP level and fecal stones with abscess formation are predictors of NOM failure, but that recurrence may not be affected by the severity of previous appendicitis.