Acute appendicitis: sonographic criteria based on 250 cases.

Two hundred and fifty consecutive patients with suspected appendicitis were examined with graded compression sonography. The initial diagnostic criterion for appendicitis was visualization of a noncompressible appendix; this was later modified to include the dimensions of the visualized appendix. The appendix was visualized in 91 of 250 patients (36%). Five adult patients with sonographically visible appendixes that were 6 mm or less in maximal diameter had either benign clinical follow-up (three patients) or a histologically normal appendix removed at surgery (two patients). However, two patients with appendixes measuring 6 mm in diameter and multiple appendicoliths had surgically confirmed acute appendicitis. Of 84 patients with visible appendixes measuring greater than 6 mm in maximal diameter, 78 had surgically confirmed acute appendicitis. In the remaining six, symptoms resolved spontaneously, and no surgery was required. In the absence of compelling clinical findings or an appendicolith, adult patients with maximal appendiceal diameters of 6 mm or less should undergo a period of close observation rather than immediate surgery. A diagnosis of appendicitis can be made in adult patients with persistent right lower quadrant pain and a visualized appendix greater than 6 mm in diameter.