Imaging of acute appendicitis: US as the primary imaging modality

Background: The investigation of the acute abdomen in infants and children has evolved during the last two decades, placing imagers at the forefront of the evaluation and diagnosis of acute right lower quadrant abdominal problems. US and CT have recently been shown to be equally accurate in the diagnosis of acute appendicitis, but not everyone agrees. Objective: To demonstrate the efficacy of triaging patients with acute abdominal problems that suggest appendicitis with US as the primary imaging modality. Materials and methods: We retrospectively reviewed the prospective imaging diagnoses in 622 children who presented to our emergency room (ER) and clinics with acute abdominal symptoms suggestive of appendicitis. We documented whether US or CT was performed and noted the diagnoses made. All of the patients had plain films. In addition, all patients undergoing surgical appendectomy during this time were also documented so as not to miss any cases of appendicitis. None was missed. Results: There were 622 consecutive patients in our study. Three patients, diagnosed as normal, were eventually excluded because of lack of follow-up. In all, 152 patients were evaluated clinically and with plain films only. They were not subject to surgical exploration or further imaging. None returned with appendicitis. Eighty-one patients were directly subject to laparotomy after clinical and plain film evaluation. Of these patients, 20% had a normal appendix. Of the remaining 389 patients, 386 had US and three had CT alone. Four patients had both CT and US because of an inconclusive US examination. Three patients had CT alone because of their size. In total, 137 patients were diagnosed with appendicitis with US and/or CT. Four of these patients (3%) had normal appendices. Forty-two patients (less three lost to follow-up) were diagnosed as normal, and none returned with findings of appendicitis. Nine others had conditions other than acute appendicitis. Three had surgically proven, nonrelated conditions, and of the other six, one had pancreatitis and five nonsurgical adnexal problems. In all, 201 patients were diagnosed (with US) with mesenteric adenitis-enteritis, and none returned with findings of appendicitis. Conclusion: We attained a high degree of diagnostic accuracy in patients presenting with findings suggestive of appendicitis using US as the primary imaging modality. Our false-positive appendectomy rate was 3%. Therefore, triage of the acute abdomen with US supported by CT when required has considerable merit, especially when considering that US is noninvasive and does not use ionizing radiation.