Factors affecting perception of the normal pediatric appendix on sonography

Background: To determine if an inherent perception skill along with sonographer experience, knowledge base, scanning time play a role in the identification of the normal appendix in the pediatric population. This is a retrospective review of pediatric (< 18 years old) patients with a clinical suspicion of acute appendicitis presenting to the emergency department of two affiliated academic tertiary care hospitals over a 1-year time span. All patients had a sonogram performed by 1/15 sonographers or by 1/8 on-call radiology residents. Those with a normal or non-visualized appendix with subsequent discharge from ER were included in the study. Patient demographics, minutes spent scanning, and sonographer years of experience in general abdominal scanning and residents level of training were recorded.

Results: Of the 127 patients included in the study, 51 (40%) were male and 76 (60%) were female, with a mean age of 11.8 ± 4.2 years. Sonographers who failed to see a normal appendix had less experience (median 8 years) than those who did visualize the appendix (median 15 years), p ≤ 0.001. Longer time spent scanning was also associated with visualizing a normal appendix (20.4 versus 29.1 min, p = 0.001). In multivariable logistic regression, more time spent scanning (OR 1.04, 95% CI 1.01, 1.07, p = 0.012) and increased sonographer experience (OR 1.07, 95% CI 1.02, 1.13, p = 0.012) resulted in greater odds of perceiving the appendix. The top 4 were significantly more likely to visualize the appendix (88.0%) than all of the other combined (20.8%, p < 0.001), and they also had substantially more experience (median 15 years versus 8 years, p < 0.001). Overall, sonographers were more likely to see a normal appendix (61%) than the residents (14%), p < 0.001.

Conclusion: Sonography to rule out appendicitis in the pediatric patient is in general most successful when performed by experienced sonographers with adequate time to perform the scan. Triaging patients to those sonographers who have displayed optimal perceptual ability of the normal appendix may help optimize patient care and hospital resources. Having experienced sonographers available after hours would allow for optimal care in the setting of 'query' appendicitis.