Routine interval appendectomy is not justified after initial nonoperative treatment of acute appendicitis.

BACKGROUND: The role of interval appendectomy (IA) after an episode of acute appendicitis is debated.

HYPOTHESIS: Patients treated nonoperatively for acute appendicitis do not require routine IA.

DESIGN: Retrospective cohort study using discharge abstract data.

SETTING: Twelve regional Kaiser Permanente hospitals in Southern California.

PATIENTS: A total of 32 938 patients were hospitalized with acute appendicitis.

INTERVENTIONS: Appendectomy or nonoperative treatment with or without abscess drainage.

MAIN OUTCOME MEASURES: Hospitalization for recurrent appendicitis or IA.

RESULTS: The type of appendicitis was abscess in 7% of patients, peritonitis in 18%, and no peritonitis or abscess in 75%. Emergency appendectomy was performed in 31 926 (97%) patients. Nonoperative treatment was used initially in 1012 patients (3%). Of these, 148 (15%) had an IA and the remaining 864 (85%) did not. Thirty-nine patients (5%) recurred after a median follow-up of 4 years. Using Cox regression, sex had a slight influence on recurrent appendicitis (hazard ratio males vs females = 0.52, 95% CI, 0.27-0.99, P = .05). Age, Charlson comorbidity index, type of appendicitis, or percutaneous abscess drainage had no influence on recurrence. Median length of hospital stay was 4 days for the admission for recurrent appendicitis compared with 6 days for the IA admission (P = .006).

CONCLUSIONS: Most patients with acute appendicitis undergo appendectomy initially. For those treated nonoperatively, the recurrence rate is low. Routine IA after initial successful nonoperative treatment is not justified and should be abandoned.