To evaluate the effect of the use of ultrasonography (US) and optional computed tomography (CT) or diagnostic laparoscopy on the percentage of unnecessary appendectomies in patients with suspected acute appendicitis.

Prospective and comparison with a historical control group.

Following the introduction of ultrasound imaging as an initial step, the outcomes in all patients presenting with suspected appendicitis in the emergency department were prospectively collected during a period of 18 months (July 2006-December 2007). Results were compared to retrospectively collected data on all patients who had undergone appendectomy for acute appendicitis in 2001, before the introduction of this imaging investigation.

Of the 312 consecutive patients in the emergency department with suspected acute appendicitis, the condition was excluded in 51 patients following clinical and laboratory investigation. The diagnostic algorithm was applied in 239 of the 261 patients (92%). All of them had initial US, followed by additional CT in 75 patients (31%) and diagnostic laparoscopy in 12 patients (5%). Appendectomy was performed in 130 patients, and 8 (6%) of the appendices were shown to be healthy following pathological investigation. Before the implementation of preoperative imaging 36 of the 170 appendices (21%) were healthy. Following the introduction of imaging techniques in accordance with the guideline there was a significant reduction in the percentage of unnecessary appendectomies (21% versus 6%; p < 0,001). The complete supplementary diagnostic algorithm had a positive and negative predictive value of respectively 90% and 98% for acute appendicitis.

Structural implementation of US with optional CT and diagnostic laparoscopy in patients with suspected acute appendicitis resulted in a lower percentage of unnecessary appendectomies.