Diagnostic performance of US for suspected appendicitis: Does multi-categorical reporting provide better estimates of disease in adults, and what factors are associated with false or indeterminate results?

Highlights: • Females and absence of tenderness are associated with a false/indeterminate US. • Age, scan time, and radiologist subspecialty are not associated with US result. • Multi-categorical reporting of US provides more granular estimates of appendicitis. To identify factors associated with false or indeterminate US result for suspected appendicitis, and assess whether multi-categorical reporting of US yields more precise estimates regarding the probability of appendicitis.