Incremental diagnostic value of ultrasound in children with suspected acute appendicitis

In children with suspected acute appendicitis, ultrasound is widely used as first-line imaging, but the incremental diagnostic value of the initial ultrasound report beyond clinical and laboratory variables remains unclear.

To evaluate the diagnostic contribution of an appendicitis-compatible initial ultrasound report beyond age, Pediatric Appendicitis Score, and C-reactive protein (CRP), and to describe the role of post-ultrasound computed tomography (CT) within an ultrasound-first pathway.

This prospective single-centre cohort included children aged 3-17 years evaluated for suspected acute appendicitis between May 2025 and March 2026. The primary outcome was histopathologically confirmed appendicitis. Logistic regression compared a clinical model including age, Pediatric Appendicitis Score total, and log₂-transformed CRP with an ultrasound-extended model additionally including an appendicitis-compatible initial ultrasound report. Model performance was assessed using the area under the receiver operating characteristic curve (AUC), Brier score, likelihood-ratio testing, and DeLong comparison.

Among 135 children in the ultrasound-first cohort, 81 had histopathologically confirmed appendicitis and 54 formed the comparison group. The clinical model showed moderate apparent discrimination (AUC 0.771; 95% confidence interval 0.689-0.852; Brier 0.188). In 132 children with classifiable ultrasound reports, addition of an appendicitis-compatible initial ultrasound report increased the AUC from 0.772 to 0.912 and reduced the Brier score from 0.187 to 0.113. Post-ultrasound CT was performed in 52/135 children (38.5%); 29 had appendicitis and 23 did not undergo appendectomy.

A clear appendicitis-compatible initial ultrasound report provided substantial incremental diagnostic information when added to age, Pediatric Appendicitis Score, and CRP, supporting its role as an integrated component of the diagnostic assessment rather than a standalone test.