Ultrasonography for the diagnosis of acute appendicitis.

Acute appendicitis is usually encountered clinically as acute abdomen. Typical cases are easy to diagnose, but it can sometimes be very difficult to make a diagnosis in atypical cases. We retrospectively studied patients who underwent ultrasonography for right-sided lower abdominal pain suggesting acute appendicitis, and assessed the accuracy of ultrasonic diagnosis. The subjects were 202 patients (100 males and 102 females) aged 6-89 years (mean: 33.3 years). From the ultrasonic findings, appendicitis was classified as follows: 1) catarrhal: a clear layer structure of the appendiceal wall and mucosal edema; 2) phlegmonous: an ill-defined layer structure of the appendiceal wall, moderate enlargement of the apendix, and maximum transverse dimension of > or = 10 mm; and 3) gangrenous: unidentifiable layer structure of the appendiceal wall and marked enlargement to form a mass. The appendix was visualized in 142 of the 202 patients (70.3 %). When the appendix was detected, the sensitivity, specificity and accuracy of ultrasound for making a diagnosis of appendicitis were 97.6%, 82.0 %, 91.5 %, respectively. With regard to assessment of the severity of inflammation, ultrasonic and histologic findings were concordant in 61.2 % of the patients. However, ultrasound was shown to possibly underestimate the extent of inflammation. On the other hand, 11 of the 60 patients with an undetectable appendix (18.3 %) were clinically diagnosed as having appendicitis. The pathologic diagnosis was catarrhal appendicitis in 3 patients and phlegmonous appendicitis in 8 patients. In patients with an undetectable appendix, the possibility of catarrhal or phlegmonous appendicitis should be kept in mind.