Integration of ultrasound findings and a clinical score in the diagnostic evaluation of pediatric appendicitis.

OBJECTIVE

To determine the predictive value of ultrasonography (US) for appendicitis in children when combined with clinical assessment based on the Pediatric Appendicitis Score (PAS).

STUDY DESIGN

Observational study of children aged 3-18 years who had an US examination for possible appendicitis. A PAS was calculated on the basis of historical elements, examination, and laboratory studies and was used to classify patients into 3 risk groups (low, medium, high). The predictive value of the PAS for appendicitis was calculated and stratified by the result of the US (positive, negative, or equivocal).

RESULTS

A total of 728 children with a median age 11.7 (IQR 7.8-14.9) years were studied; 29% had appendicitis. The negative predictive value of US decreased with increasing PAS-based risk assignment: low risk 1.00 (95% CI, 0.97-1.00), medium risk 0.94 (0.91-0.97), and high risk 0.81 (0.73-0.89). With increasing PAS, the positive predictive value increased: low risk 0.73 (0.47-0.99), medium risk 0.90 (0.82-0.98), and high risk 0.97 (0.95-1.0). Among children with equivocal ultrasound results, the proportion with appendicitis ranged from 0.09 (0.0-0.19) for low-risk patients to 0.47 (0.33-0.61) among for high-risk patients.

CONCLUSION

Ultrasound findings in children with possible appendicitis should be integrated with clinical assessment, such as a clinical score, to determine next steps in management. Rates of false-negative US increase with increasing PAS, and false-positive US results occur more often with lower PAS. When discordance exists between US results and the clinical assessment, serial examinations or further imaging are warranted.