Sonography in acute appendicitis: diagnostic utility and influence upon management and outcome

A study is made of the diagnostic utility of echography in clinically suspected appendicitis, and its influence upon patient management and outcome. A total of 374 consecutive patients with possible appendicitis were prospectively evaluated by ultrasound. Two groups were established: group A (high clinical probability, > or =0.70) and group B (moderate clinical probability, 0.20-0.60). In group-A patients (n = 105, 28%), prevalence of appendicitis = 0.90) underwent surgery regardless of the echographic findings. In group B (n = 269, 72%), prevalence of appendicitis = 0.28) surgery was performed in the event of positive echography, whereas negative echographic findings did not definitively discard appendicitis. The diagnostic utility of echography was evaluated by applying the Pauker-Kasirer threshold approach to clinical decision making. The influence of ultrasound upon outcome was in turn evaluated by contrasting the total appendectomized patients (190 of 374) with a series of 181 individuals subjected to appendectomy prior to the introduction of echography. The probability of appendicitis in the presence of positive echography was 0.95 in group A (sensitivity = 0.92) and 0.89 in group B (sensitivity = 0.91). The probability of appendicitis in the event of negative ultrasound was 0.58 in group A (specificity = 0.55) and 0.03 in group B (specificity = 0.95) . In 46% of cases the echographic findings led to a change in therapeutic regimen. In addition, the incidence of negative appendectomies was significantly reduced (19.3 vs 11.6% with echography; p = 0.03), as was the delay in establishing a diagnosis (under 6 h in 68.5 vs 84.2% with echography; p = 0.002) and the number of medical acts required (three in 71.3 vs 84.1% with echography; p = 0.001). There was no significant reduction in the incidence of perforated appendicitis (17.1 vs 17.9% with echography), in the number of postoperative complications (13.8 vs 7.6% with echography), or in the days of hospital stay (4.44 vs 4.80 with echography). Echography proved useful in group B, and was generally of little utility in group A. The technique had a positive influence on treatment, with management reorientation in a considerable number of patients, and on outcome, since ultrasound contributed to establishing an earlier diagnosis, with a reduction of unnecessary appendectomies.