Risk Factors for False-Positive Ultrasound in Pediatric Acute Appendicitis: A Prospective Cohort Study.

OBJECTIVES: To identify independent predictors of false-positive ultrasound (US) in children evaluated for suspected appendicitis. METHODS: A prospective cohort study was conducted from 1 January 2022 to 31 October 2025 including children presenting with suspected appendicitis whose initial abdominal US was positive. Final diagnosis was determined by histopathology in operated patients and structured clinical follow-up in non-operated patients. Multivariable logistic regression identified independent predictors of false-positive US. RESULTS: Among 1174 children assessed, 564 had a positive US and were included. Of these, 81 (14.4%) were ultimately classified as false-positive. The negative appendectomy rate was 7.6%. The mean age was 9.5 ± 2.6 y and males accounted for 64.9% of the cohort. On multivariable analysis, four factors were independently associated with false-positive US. These factors included diarrhea (OR 2.15; p = 0.025), Alvarado score ≤ 5 (OR 2.22; p = 0.007), white blood cell count < 12 × 10⁹/L (OR 2.15; p = 0.004), and C-reactive protein ≤ 10 mg/L (OR 1.95; p = 0.016). CONCLUSIONS: False-positive US occurred in 14.4% of children with suspected appendicitis and resulted in a measurable negative appendectomy rate. Diarrhea, low Alvarado scores, and low inflammatory markers identified clinical contexts in which a positive US was less likely to correspond to true surgical disease. Incorporating these factors into diagnostic decision-making may reduce unnecessary appendectomy and support safe observation strategies.