Perforation rate after a diagnosis of uncomplicated appendicitis on CT

BACKGROUND: Appendicectomy is a common emergency operation. The aim of this analysis was to study the effect of preoperative delay on disease progression, and whether a novel scoring system (Atema score) could be useful in predicting complicated appendicitis. METHODS: Patients with uncomplicated acute appendicitis on CT and who underwent appendicectomy in 2014–2015 were analysed for patient characteristics, preoperative delay and outcomes. RESULTS: Of 837 patients with uncomplicated appendicitis 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 an Atema score of 6 or less and those with no appendicolith on CT and a C-reactive protein level below 51 mg/l were the slowest to develop perforation, reaching a perforation rate of 5 per cent in 7.1 and 7.6 h respectively. CONCLUSION: A substantial proportion of patients with uncomplicated acute appendicitis on CT have complicated appendicitis at surgery. However, in patients with no risk factors, surgery can be postponed safely for up to 7 h.