Normal appendiceal diameter on computed tomography and its influencing factors in the pediatric population

Abstract

Background: Appendicitis is the most common indication for emergency abdominal surgery in children. Computed tomography (CT) plays a crucial role in evaluating pediatric patients with suspected appendicitis. However, the literature describing the normal appendiceal diameter in the pediatric Asian population remains limited.

Objectives: This study aimed to establish reference values for normal appendiceal diameter and to identify variables influencing its diameter in pediatric patients aged 18 years or younger who underwent abdominal CT.

Methods: The study was reviewed and approved by the Institutional Review Board. We conducted a retrospective study of 358 children (≤18 years of age) who underwent abdominal CT scans between January 1, 2018, and December 31, 2022, for indications unrelated to appendicitis. Demographic data, including calculated body mass index and body surface area (BSA), were recorded. Radiologic data on the appendices included the maximal outer diameter and single-wall thickness. The data were classified into five age-based strata, and the mean appendiceal diameters were calculated. Associations between appendiceal diameter and age, and between appendiceal diameter and BSA, were assessed using linear regression models.

Results: The mean appendiceal diameter was 5.0 ± 1.1 mm. Stratified analysis by age revealed the following mean appendiceal diameters: 4.2 mm (0–1 years), 4.4 mm (1–5 years), 4.9 mm (5–10 years), 5.5 mm (10–15 years), and 5.8 mm (15–18 years). Age and BSA demonstrated significant predictive variability for appendiceal diameter (P < 0.001), explaining 35.2% and 33.1% of the variance, respectively. The regression equations were: appendiceal diameter (mm) = 4.0 + 0.1 × age (years) and appendiceal diameter (mm) = 3.7 + 0.1 × BSA (m2).

Conclusion: A uniform diameter cutoff for appendiceal diameter should not be applied across the pediatric population because the appendix grows during childhood. This study demonstrated positive correlations between the appendiceal diameter and age and between the appendiceal diameter and BSA.