The impact of ultrasound in suspected acute appendicitis

To evaluate prospectively the impact of an appendix ultrasound (US) service on the clinical management of patients presenting with suspected acute appendicitis.

The referring clinician completed a proforma for patients presenting with suspected acute appendicitis. Two visual analogue scales assessed clinical suspicion before and after knowledge of laboratory results. The clinician also indicated if they intended to operate had US been unavailable. During a 3-year period, 327 patients were examined by graded-compression US and diagnosed "positive" or "negative" for acute appendicitis. Findings were correlated with histopathology results. The referring clinician completed a retrospective audit questionnaire to assess user satisfaction.

Clinical suspicion was altered by knowledge of laboratory results. The decision to operate if US had been unavailable, was "yes" in 70 cases (group A), "no" in 231 (group B), and incomplete in 26 (group C). In group A, 31 patients (44.3%) had a negative US and 25 avoided surgery. US identified 39 cases of appendicitis and 37 appendicectomies confirmed appendicitis in 34 cases. In group B, 72 (31.2%) patients had a positive US and 66 appendicectomies confirmed 51 cases of appendicitis. The sensitivity of US was 94.7% in group A, 93.3% in group B and 93.8% overall. Specificity was 90.6% in group A, 91.2% in group B and 91.3% overall. US findings were contrary to intended surgical management in 103 cases. Management was altered in 97 cases (32.2%), with a positive outcome in 85 (28.2%). The referrers found US of appendix very useful in planning appropriate management.

US of the appendix increases diagnostic accuracy, alters management and is more sensitive and specific than clinical impression, either alone, or in conjunction with laboratory results.