ACUTE APPENDICITIS; ULTRASONOGRAPHY AS PRE-OPERATIVE SCREENING TOOL

Abstract

Objective: To determine the accuracy of ultrasonography in confirming acute appendicitis in adult patients presenting with relevant clinical features taking histopathology of removed appendix as the gold standard.

Study Design: Cross-sectional (Validation) study.

Place and Duration of Study: Radiology Department Combined Military Hospital (CMH) Rawalpindi from August 2008 to February 2009.

Material and Methods: A total of 80 cases of clinically suspected acute appendicitis selected on non probability convenience sampling technique were included in the study. They all underwent ultrasound evaluation. Sensitivity, Specificity, Positive Predictive Value (PPV) and Negative Predictive Value (NPV) of Ultrasound and Ultrasound (USG) findings were calculated keeping surgical findings and histopathology of the removed appendix as a gold standard, whenever appendectomy was carried out. SPSS version 16.0 was used to carry out necessary statistical calculations.

Results: Out of 80 patients whose ultrasound examination of right lower quadrant (RLQ) was performed, 36 patients were correctly diagnosed as having acute appendicitis on USG out of 42 finally diagnosed cases based on histopathology. Similarly we picked 18 normal appendices out of 38 non-appendicitis patients in which 6 proved to be false negative. This showed that US scan has sensitivity of 86%, specificity 80%, PPV 92%, NPV 67% and overall accuracy of 84%. The most accurate appendiceal finding for appendicitis was a diameter of 6 mm or larger followed by non compressibility of appendix.

Conclusion: Ultrasound has high diagnostic accuracy in diagnosis of acute appendicitis and helps to reduce negative appendectomy rates. A greater than 6-mm diameter of the appendix under compression is the most accurate US finding.