Purpose: Appendicoliths in appendicitis are associated with complicated appendicitis (CA) and unacceptable failure rates of non-operative management (NOM). The accuracy of ultrasound (US) in resolving appendicoliths is poorly characterised. We aimed to compare diagnostic accuracy of US to CT for appendicolith appendicitis and correlate results with pathological findings. Methodology: A multicentre, retrospective review of imaging, operative and pathology reports was performed of patients who underwent US and CT prior to appendicectomy from 2016-2024. Patients without histopathological appendicitis or appendix seen on US were excluded. Given importance of CT appendicoliths and low expected yield of pathology and operation reports, appendicolith on any of these three tests was considered the diagnostic standard. Diagnostic accuracy indices of US for appendicolith were calculated. Correlation with CA was analysed for US and CT. Findings: 44 patients fulfilled inclusion criteria. Appendicolith was identified on 9 CTs and 3 operative/histopathology reports, yielding a combined prevalence of 22.7% (10/44). US identified five appendicoliths, two of which were seen on other modalities (sensitivity 20.0%, specificity 91.2%, PPV 40.0%, NPV 79.5%). CA was identified in 15 patients (34.1%). Only CT detected appendicoliths were predictive of CA (CT - p 0.02 vs US - p 0.24). Conclusion: US missed a significant proportion of clinically important appendicoliths in our study. However, generalisability of these findings is limited by sample size and selection bias inherit to a retrospective cohorted design. Further investigation is needed to corroborate these findings given potential for avoidable treatment failure in NOM patients.