Predictive Factors of Acute Appendicitis in Children With Non-Visualized Appendix on Ultrasound: A Prospective Cohort Study.

Background: Most studies have demonstrated the high accuracy of ultrasound for the diagnosis of acute appendicitis (AA) in children. However, the lack of visualization of the appendix on ultrasound is usually a challenge. The aim of this study was to identify any factors that might help the physician make the right decision when dealing with a child with suspected appendicitis and an appendix not seen on ultrasound. Patients and Methods: After receiving Institutional Review Board approval, we conducted a prospective study in a pediatric emergency department from January 1, 2022, to December 31, 2022. All children under 14 years of age with suspected AA and an appendix not visualized on ultrasound were included. Results: During the study period, 333 children presented with suspected AA. Of these patients, 106 had an appendix not seen on ultrasound. Our patients' median age was 10 years (interquartile range [IQR], 8-11 years), with 54.7% (n = 58) of children being female. Twenty-five (23.6%) were ultimately diagnosed with AA based on pathologic examination. Multivariable logistic regression analysis revealed that Alvarado score ≥6 and increased peri-appendiceal fat echogenicity were predictive for AA. The combination of these two factors provided a positive predictive value of 100%. A white blood cell (WBC) count ≤10 × 109/L and/or a C-reactive protein (CRP) level ≤6 mg/L makes the diagnosis of appendicitis unlikely. Conclusions: In conclusion, our study demonstrated that an Alvarado score at or above six and increased peri-appendiceal fat echogenicity are independent predictive factors of AA in children with non-visualized appendix on ultrasound. The combination of these two factors would confirm the diagnosis of AA in these patients.