Background: Randomized studies have indicated that acute appendicitis may be treated by antibiotics without the need of surgery. However, concerns have been raised about selection bias of patients in such studies. Therefore, the present study was aimed to validate previous findings in randomized studies by a full-scale population-based application.

Methods: All patients with acute appendicitis at Sahlgrenska University Hospital (May 2009 and February 2010) were offered intravenous piperacillin plus tazobactam according to our previous experience, followed by 9 days out-hospital oral ciprofloxacin plus metronidazole. Endpoints were treatment efficacy and complications. Efficient antibiotic treatment was defined as recovery without the need of surgery beyond 1 year of follow-up.

Results: A total of 558 consecutive patients were hospitalized and treated due to acute appendicitis. Seventy-nine percent (n = 442) received antibiotics as first-line therapy and 20 % (n = 111) had primary surgery as the second-line therapy. Seventy-seven percent of patients on primary antibiotics recovered while 23 % (n = 100) had subsequent appendectomy due to failed initial treatment on antibiotics. Thirty-eight patients (11 %) of the 342 had experienced recurrent appendicitis at 1-year follow-up. Primary antibiotic treatment had fewer complications compared to primary surgery.

Conclusions: This population-based study confirms previous results of randomized studies. Antibiotic treatment can be offered as the first-line therapy to a majority of unselected patients with acute appendicitis without medical drawbacks other than the unknown risk for long-term relapse, which must be weighed against the unpredicted but well-known risk for serious major complications following surgical intervention.