Indication of conservative treatment by antibiotics for uncomplicated and complicated acute appendicitis.

Background: Acute appendicitis is one of the most common emergency abdominal disease, and recent studies have evaluated conservative treatment using antibiotics for uncomplicated appendicitis. Although the efficacy of conservative treatment for uncomplicated appendicitis is known, its efficacy for complicated appendicitis remains unknown, so are risk factors for the conservative treatment of appendicitis. In our institution, conservative treatment has long been the first choice for most appendicitis cases, except for perforation. Therefore, this novel study investigated the outcomes of conservative treatment for uncomplicated and complicated acute appendicitis and the risk factors associated with conservative treatment.

Aim: To investigate the indication of conservative treatment by antibiotics for uncomplicated and complicated acute appendicitis.

Methods: We investigated 270 patients who received conservative treatment for acute appendicitis at the Nishitokyo Central General Hospital, between April 2011 and February 2022. Twenty-eight (10.3%) patients were resistant to conservative treatment and underwent surgery. We retrospectively investigated the outcomes of conservative treatment for appendicitis and the risk factors for resistance to conservative treatment using the receiver operating characteristic curves and Cox hazard model.

Results: Two hundred and forty-two (89.7%) patients improved with conservative treatment. The significant and independent predictors of resistance to conservative treatment were body temperature ≥ 37.3 °C, appendicolith and Douglas sinus fluid visible on computed tomography (CT). The rate of resistance to conservative treatment was 66.7% (6/9) for patients with the above three factors, 22.9% (8/35) for patients with two factors (appendicolith and body temperature ≥ 37.3 °C), 16.7% (2/12) for patients with two factors (Douglas sinus fluid and appendicolith) and 11.1% (1/9) for patients with two factors (Douglas sinus fluid and body temperature ≥ 37.3 °C).

Conclusion: A temperature ≥ 37.3 °C, appendicolith and Douglas sinus fluid on CT might be clinical risk factors of resistance to conservative treatment for acute appendicitis.