Appendiceal neoplasm rate in acute appendicitis and long-term outcomes after antibiotics for uncomplicated acute appendicitis

Acute appendicitis is one of the most common abdominal emergencies now recognized to present as two different forms of severity, uncomplicated and complicated acute appendicitis. Appendectomy has been a standard treatment for acute appendicitis for the last 120 years, but recent randomized clinical trials (RCTs) have demonstrated the effectiveness of antibiotics in the treatment of uncomplicated acute appendicitis also at longer-term. One concern regarding non-operative management is the potential risk of missing an underlying appendiceal malignancy. Appendiceal tumor risk has been shown to increase with appendicitis severity. Appendiceal neoplasms associated with uncomplicated acute appendicitis are rare, but recent studies have reported an alarming rate of appendiceal tumors associated with complicated acute appendicitis presenting with a periappendicular abscess.

The aim of this thesis was to assess the long-term prevalence of appendiceal tumors both in uncomplicated and complicated acute appendicitis, with a special focus on the tumor prevalence in patients with a periappendicular abscess. Additionally, the aim was to assess the long-term results of antibiotic therapy in the treatment of uncomplicated acute appendicitis with both aims further supporting the optimization of different treatment strategies for acute appendicitis.

The prevalence of appendiceal tumors associated with periappendicular abscess was high (14.3%) and markedly higher compared with both uncomplicated and complicated acute appendicitis without periappendicular abscess. All but one patient with a periappendicular abscess and a tumor were over 35 years of age. The results highlight the need for routine interval appendectomy at least in patients over 35 years. The prevalence of appendiceal tumors in uncomplicated acute appendicitis was low in both the prospective cohort study and the RCT 10-year follow-up. At 10 years, 44.3% of the antibiotic treated patients had undergone appendectomy and the true appendicitis recurrence rate was 37.8%. Thus, more than half of the patients were treated conservatively without surgery. These findings support the safety and efficacy of antibiotics for uncomplicated acute appendicitis.