Researchers examined the reliability of existing risk prediction models in recognizing patients presenting to hospitals in the UK with acute right iliac fossa pain who are at low risk of appendicitis. They identified some 5,345 patients [3,613 (67·6%) were women] across 154 UK hospitals and performing a systematic search, they identified 15 validated risk prediction models. Findings suggest a disproportionate risk of admission without surgical intervention and high rates of normal appendicectomy among women in the UK. Of the models identified, the Adult Appendicitis Score performed best (cut-off score 8 or less, specificity 63·1%, failure rate 3·7%) and the Appendicitis Inflammatory Response Score performed best for men (cut-off score 2 or less, specificity 24·7%, failure rate 2·4%).