Adjunct ultrasonography in children with suspected acute appendicitis: identifying the optimal target group.

Background: Role of ultrasonography in diagnosis of acute appendicitis in children is being debated. This study was conducted ahead of a clinical trial and aimed to evaluate the adjunctive role of ultrasonography in this group.

Methods: Retrospective chart review of consecutive children undergoing appendicectomy in an Australian tertiary children's hospital over 24 months. Two study groups were: clinical assessment and clinical assessment plus ultrasonography. The accuracy of diagnosis was compared by generating estimates for sensitivity and positive predictive value using histopathology of the appendix as the reference standard. The incremental value of ultrasonography was evaluated in subgroups of gender, age and clinical severity.

Results: Two hundred ninety-five children (170 boys, median age 10 years) were included in the study. Negative appendicectomy rate was 17.3%; 10.4% in the clinical assessment group (n = 134) and 23% in the ultrasonography group (n = 161). Overall sensitivity for diagnosis by clinical assessment (71.4%, 95% confidence interval (CI) 63.3-79.5) was not significantly different to that using adjunct ultrasonography (77.7%, 95% CI 69.7-85.7; P = 0.29). Adjunct ultrasonography was more sensitive between 7 and 11 years (81% versus 68%, P = 0.002) and possibly in girls (86% versus 73%, P = 0.1), but did not increase the sensitivity of the diagnosis in children who presented with milder symptoms and signs.

Conclusions: Adjunct ultrasonography may not increase the overall accuracy of diagnosis of acute appendicitis in children but holds promise in certain subgroups viz. between 7 and 11 years and in girls. There is an increase in negative appendicectomies following a 'non-targeted' use of ultrasonography. Future prospective trials should take cognizance of these findings in designing the subgroup analysis.