6 The Value of Ultrasound in Diagnosing Acute Appendicitis

Aim The diagnosis of acute appendicitis relies on a thorough history and examination and can often be challenging. Ultrasound is widely considered to be the most appropriate first line investigation; however non-diagnostic ultrasounds are not uncommon and do lead to delays in diagnosis and/or definitive treatment by creating a need for further clinical assessment. The purpose of this study was to determine the sensitivity and specificity of ultrasound diagnosis of appendicitis in patient treated at Doncaster Royal Infirmary, and to determine the local negative appendicectomy rate. Method This was a retrospective analysis of 99 patients undergoing appendicectomy, with a prior ultrasound abdomen within one week of the procedure being undertaken. Data was collected from review of patient's hospital medical records (discharge summaries, clinic letters, PACs). Results 99 patient aged 8-76 years were studied. Male to female ratios was 3:1. The sensitivity and specificity of ultrasound was 16% (95% CI - 7% to 29%) and 96% (95% CI - 86% to 99%) respectively with PPV of 80% and NPV of 52%. The accuracy of ultrasound diagnosis was found to be 55% (95% CI 44% to 65%). The negative appendicectomy rate was 48%. Conclusions From our study, ultrasound cannot reliably identify nor exclude appendicitis. Less than 16% of patients who had proven appendicitis (positive histology) had scans that indicated. Almost 50% of the normal/indeterminate scans were false negatives. Furthermore, 20% of positive ultrasound reports were false positives. A collaborative quality improvement project with the imaging department is planned to address these findings.