Fig. 2.

Kaplan–Meier one minus survival curves estimating the rate of complicated appendicitis

a All patients; b patients according to Atema score 0-6 or 7-22; c patients divided according to C-reactive protein (CRP) level of 0-50, 51-100 or more than 100 mg/l; d patients with or without appendicolith on CT. b  P<0.001; c  P<0.001 (CRP >100 versus CRP 0-50 and CRP 51-100), P=0.044 (CRP 0-50 versus CRP 51-100); d  P<0.001 (log rank test).

Of a total of 837 patients with uncomplicated appendicitis diagnosed on CT, 187 (22.3 per cent) were found to have complicated appendicitis at surgery. The median time estimate for perforation was 25.4 h after CT, with an hourly rate of perforation of 2 per cent. Patients with low Atema score, low C-reactive protein level and no appendicolith had lower perforation rates.