Low diagnostic values of ultrasonography and negative appendectomy: still a major problem in university hospitals

Background: Misdiagnosis of the acute appendicitis may increase the rate of negative appendectomies, which involve a huge waste of resources and are sometimes associated with severe complications. Furthermore, false negative result of ultrasonography (US) could lead to perforation of appendix. Since ultrasonography is still the most common imaging technique used in Iranian appendicitis patients, the study focused on evaluate the accuracy of ultrasonograghy in an educational hospital in Iran. Methods: We retrospectively reviewed the results of ultrasonograghy in 270 patients who referred to Rasoul-e-Akram hospital in Tehran, Iran, between April 2002 and October 2004 with acute abdominal symptoms suggestive of appendicitis. The results of ultrasonography were compared with the histopathologic reports of biopsies as a gold standard. In data analysis Chi-square, independent t-test and Mann- Whitney U-test were performed. Results: The accuracy of ultrasonograghy in acute appendicitis was 60.4% and the rate of negative appendectomy was 17.4%. Diagnostic values of US were calculated as the sensitivity of 55.4% [95% confidence interval (CI)=48.6-62], specificity of 72.3% (95%CI=57.1-83.9), positive predictable value (PPV) of 90.4% (95%CI= 83.9-94.6) and negative predictable value (NPV) 25.6% (95%CI=18.6-34). Conclusion: Although the results of our study implied that the diagnostic values of ultrasonography were not considerable, but it is still the only imaging techniques available for patients in Iran. In reference to the low NPV, using an alternative technique such as abdominal CT scan is recommended. More attention must be paid on the signs and symptoms related to acute appendicitis in such patients especially in teaching hospitals.