Background and aims Appendicitis is the most common surgical emergency in children yet the diagnostic workup of children varies greatly among major centres internationally. Once heralded as a revolution in diagnosis, the results of its clinical application have been conflicting. Intra-operator variability has a significant effect on appendix visualisation, with some centres quoting visualisation rates as high as 80% and as others as low as 30%. We had anecdotally observed that many ultrasounds ordered at our centre were not visualising the appendix and wanted to determine our visualisation rate and how it affects the utility of ultrasound in clinical practice.

Methods 10 year retrospective review of all children, presenting to the Canberra Hospital with right sided or periumbilical abdominal pain between 2002 and 2012, where ultrasonography was utilised in the confirmation or refutation of appendicitis as a diagnosis.

Results 737 ultrasound scans were reviewed. Rates of ultrasonography doubled over the period but appendix visualisation rate dropped from 42% to 25%. Sensitivity is 96% when the appendix was visualised for all tests but only 71% when a negative result included non-visualised test. The incidence of appendicitis was 21% in the total cohort, and 6% in the non-visualisation group.

Conclusion Ultrasonography is a theoretically appealing tool for paediatric appendicitis, if and only if, the appendix is visualised. If the incidence of appendicitis in the non-visualised group approaches that of the general population, a non-visualised test provides no reassurance whatsoever, and appendicitis remains a diagnostic phantom for the clinician.