We attempt to determine the ultrasonographic diagnostic criterion for choosing between operative and conservative therapy by the fuzzy theory.
1) 37 cases of acute appendicitis treated surgically after an ultrasonographic examination, were evalu-ated in regard to seven findings: margin, swelling, wall thickness, bending, foreign body, and peritoneal effusion, to determine the diagnostic criterion of the operative or conservative therapy. The accuracy rate of this criterion was 83%. and superior to leukocyte cell count and body temperature.
2) 16 patients who received conservative therapy were evaluated by this criterion. The patients who were successful in conservative therapy were diagnosed correctly by the ultrasonography, but 2 patients who received operation changed for operative indication by following ultrasonography.