Accuracy of ultrasonography in diagnosis of acute appendicitis at King Chulalongkorn Memorial Hospital

Abstract

Background: Acute appendicitis is one of the most common emergency abdominal surgical condition with a yearly incidence rate of approximately 140 per 100,000 persons in Thailand between 2014 to 2017. The diagnosis of appendicitis is mainly relied on clinical manifestations, but these diagnostic approaches are not always accurate. Imaging tests such as graded compression ultrasonography (US) and computed tomography (CT) have become more commonly used to improve the diagnostic performance.

Objective: To evaluate the sensitivity, specificity and predictive values of US in the diagnosis of acute appendicitis at King Chulalongkorn Memorial Hospital (KCMH).

Methods: We retrospectively gathered data from the records of 85 adult patients, suspected acute appendicitis and underwent abdominal US at KCMH between January 2010 and December 2017. We collected patient’s demographic data, clinical history, laboratory findings, US report and subsequent CT imaging, surgical report and pathological findings. Surgical record and histopathologic analysis were the reference standard.

Results: Overall, US had sensitivity 69.0% (95% CI, 49.2 – 84.7), specificity 89.3% (95% CI, 78.1 – 96.0), accuracy 82.4% (95% CI, 72.6 – 89.8), positive predictive value (PPV) 76.9% (95% CI, 56.4 – 91.0) and negative predictive values (NPV) 84.7% (95% CI, 73.0 – 92.8) for the diagnosis of acute appendicitis in adult patients. The enlarged appendix diameter 6 mm finding showed the highest sensitivity, accuracy and NPV.

Conclusion: US might be useful imaging modality to diagnose acute appendicitis in adult patients not just in some specific condition. The evidence of enlarged appendix diameter 6 mm is the most accurate appendiceal finding for the diagnosis of acute appendicitis.