Sonography of acute appendicitis: a critical review

In 20% of the cases of acute appendicitis, especially in children, the elderly, and ovulating women, the findings are atypical. The radiographic procedures used to aid in the diagnosis have not been proven reliable. Sonography has often been used to diagnose or rule out appendiceal abscesses, or diseases that can mimic acute appendicitis, such as gynecologic, obstetric, or biliary abnormalities. Recently, high-resolution sonography with graded compression has been shown to be very helpful in the diagnosis of acute appendicitis in several studies. High-resolution 5- to 7.5-MHz transducers are used to compress the bowels, displace the interfering gas in the right lower quadrant, and directly visualize the inflamed appendix with a sensitivity that varies from 80 to 95%, a specificity of 95 to 100%, and an accuracy of 91 to 95%. It is also possible to differentiate acute appendicitis from the gangrenous and perforated appendix. High-resolution sonography is currently the diagnostic method of choice for appendicitis, particularly in patients with equivocal clinical findings. The technique, normal and pathologic anatomy values, and limitations of sonography are discussed.