Ultrasound in the differential diagnosis of appendicitis.

The purpose of this study was to determine the accuracy of sonography in detecting diseases other than appendicitis in the clinical setting of suspected appendicitis. Six hundred and nine patients were evaluated using graded compression ultrasound (US). A broad spectrum of diseases was suggested in the group of patients who eventually turned out not to have appendicitis (n = 426), including gastrointestinal (154), gynaecological (32), biliary (11), urological (8), and miscellaneous (5) abnormalities. However, out of these there were three cases of incorrect sonographic diagnoses with serious sequelae. Appendicitis coincidental with another disease capable in itself of explaining the patients' symptoms was confirmed in seven out of 10 patients where sonographically suggested; in six patients out of this group only the suggested alternative condition was held responsible for the symptoms while the inflamed appendix was overlooked. US is of considerable value in establishing alternative diagnoses in patients with equivocal signs of appendicitis. However, one should always consider the possibility of co-existing appendicitis in patients where US has revealed another condition which could be held in itself responsible for the patient's symptoms.