Presence of Sonographic Secondary Signs Without Visualization of Appendix Is Indicative of Appendicitis in Children Younger Than 5 Years.

Purpose: Diagnosis of acute appendicitis is more difficult in children aged 0-4 years due to atypical clinical presentation, leading to delay in diagnosis and higher incidence of complications. Nonvisualization of the appendix on ultrasound increases diagnostic challenge. We examined the utility of standardized reporting of sonographic secondary signs of appendicitis in children younger than 5 years with nonvisualization of the appendix.

Methods: A retrospective cohort study of children younger than 5 years who underwent appendectomy following nonvisualization of the appendix on ultrasound from 2016 to 2022 was performed. Primary outcome was comparison of ultrasound and intraoperative findings. Two-sample t test and Wilcoxon sum-rank test compared continuous variables, and Fisher exact test compared categorical variables. Univariate and multivariate logistic regression analyses were performed to assess risk factors for complicated appendicitis in those with category 3 ultrasounds.

Results: Overall, 92 patients whose appendix was not visualized on ultrasound were included: 26 without secondary signs (category 2) and 66 with secondary signs (category 3). Significant differences in intraoperative findings between category 2 and category 3 patients existed (P < 0.001). On intraoperative assessment of patients with ultrasound category 2, 3.8% had no appendicitis, 46.2% had simple appendicitis, 34.6% had complicated appendicitis, and 15.4% underwent interval appendectomy. Conversely, of category 3 patients, 0% had no appendicitis, 7.6% had simple appendicitis, 48.5% had complicated appendicitis, and 43.9% underwent interval appendectomy. On logistic regression, in children with category 3 ultrasounds, presence of both fluid collection and free fluid as secondary signs was associated with intraoperative findings of complicated appendicitis. However, number of secondary signs was not significantly associated with increased likelihood of complicated appendicitis intraoperatively.

Conclusion: Presence of secondary signs without visualization of the appendix was shown to be indicative of appendicitis, with high suspicion for complicated appendicitis, in patients younger than 5 years. Further validation of the presence of secondary signs on right-lower-quadrant ultrasound may lead to more expedient diagnosis, reduction in cross-sectional imaging, and earlier treatment of complicated appendicitis.