Compression ultrasonography as an aid in the differential diagnosis of appendicitis.

Conventional diagnostic tools have hitherto demonstrated low levels of specificity in establishing the diagnosis of appendicitis. We conducted a retrospective study of all patients who underwent abdominal or pelvic compression ultrasonography during a 15 month period based on variable clinical suspicion of appendicitis. Ultrasonographic interpretations were correlated with surgical and pathologic findings and clinical follow-up study. The initial 76 prospective ultrasonographic readings, interpreted by multiple examiners, were labeled group 1. The criterion used to diagnose appendicitis in this group was visualization of a noncompressible target-like structure with a hypoechoic wall greater than 2 millimeters in diameter. Ultrasonography was found to be 66.7 per cent sensitive, 90.6 per cent specific and 86.8 per cent accurate in the diagnosis of appendicitis, with a positive predictive value of 57.1 per cent and a negative predictive value of 93.5 per cent. We reassembled 70 of the original ultrasonographic examinations and retrospectively reanalyzed these studies (group 2), using the most recently published criterion, which requires a maximal appendiceal diameter of greater than 6 millimeters. Ultrasonography was shown to be 80.0 per cent sensitive, 95.0 per cent specific and 92.9 per cent accurate in diagnosing appendicitis, with a positive predictive value of 72.7 per cent and a negative predictive value of 96.6 per cent. Ultrasonographic examination provided additional findings, predominantly gynecologic or obstetric, in 52 per cent of the women, leading to an alternative diagnosis in one-third of these patients with complaints of abdominal pain. Ultrasonographic study provided additional findings in 12 per cent of the men, leading to alternative diagnoses in 12 per cent. Ultrasonographic results directly influenced clinical management in 18 per cent of the patients. As suggested in the most recent literature, appendiceal ultrasonographic examination is a reliable ancillary technique in diagnosing or excluding appendicitis. It is indicated only in patients with an atypical or equivocal presentation; those with clinical grounds do not require ancillary diagnostic aids and should proceed immediately to surgical intervention. The predominant role of ultrasonography in evaluating appendicitis is not as an independent diagnostic determinant. Instead, it is most useful as a means of improving decision making when considered in combination with a thorough history and physical examination in those patients who represent diagnostic dilemmas.