Selective imaging strategies for the diagnosis of appendicitis in children.

BACKGROUND We previously reported an appendiceal imaging protocol in which children with equivocal clinical presentations for acute appendicitis undergo ultrasonography (US) followed by computed tomography (CT). However, risk groups of children who would benefit most from imaging studies have not been established. OBJECTIVE To define and test selective imaging guidelines to increase diagnostic accuracy and reduce unnecessary testing for children with suspected appendicitis. METHODS We modeled outcomes under 3 different management guidelines. Patients were risk-stratified by a recursive partitioning analysis of a retrospective cohort. Subjects included children with equivocal presentations of acute appendicitis evaluated between January 1996 and December 1999. By using recursive partitioning, 3 risk groups were identified: low, medium, and high risk for acute appendicitis. Three imaging guidelines were defined. Under the first guideline, representing standard clinical practice at Children's Hospital Boston at the time of the study, all children with equivocal signs and symptoms for acute appendicitis undergo US first. If the US is positive, the child proceeds to appendectomy. If the US is negative, the child undergoes CT. Under guideline 2, low-risk children undergo US and, if negative, are discharged from the hospital. High-risk children undergo CT, and medium-risk children undergo US followed by CT. Under the third guideline, low-risk children undergo no imaging and are admitted for observation. High-risk children proceed directly to appendectomy without imaging studies. Medium-risk children undergo US followed by CT. Clinical outcomes and the number of imaging studies performed were modeled under current practice and under each guideline. RESULTS Identified were 1401 cases of equivocal appendicitis; 958 (68.4%) with complete data. The mean age was 11 +/- 4.3 years. Of 958 children, 588 (61.4%) had acute appendicitis. One hundred forty-three patients were in the low-risk group, defined as neutrophils <or=67%, bands <5%, and no guarding on abdominal examination. Fifteen (10%) children had appendicitis. Two hundred twenty-five were high-risk for appendicitis defined as neutrophils >67%, white blood cell count >10,000/mm(3), guarding, and abdominal pain >13 hours. Of these, 202 (90%) had appendicitis. Under guideline 1, there were 22 negative appendectomies, 35 missed or delayed diagnoses, and 958 USs and 673 CT scans performed. Under guideline 2, there would have been 23 negative appendectomies, 36 missed or delayed diagnoses, and 733 USs and 637 CT scans performed. Under guideline 3, there would have been 36 negative appendectomies, 37 missed or delayed diagnoses, and 590 USs and 412 CT scans performed. CONCLUSIONS Selective imaging guidelines can reduce the number of radiographic studies performed with minimal diminution in accuracy of diagnosis of pediatric appendicitis.