Appendicitis: CT Scan vs Ultrasound Depends on Hospital Type

Yael Waknine

December 24, 2012

Community hospitals are more than 4 times more likely than pediatric institutions to use radiation-exposing computed tomography (CT) scans and 80% less likely to use ultrasound for pre-appendectomy evaluations in children, study results suggest.

Jacqueline M. Saito, MD, MSCI, and colleagues from Washington University School of Medicine in St. Louis, Missouri, also found that both diagnostic tools were less sensitive for appendicitis in the community hospital setting.

As previously reported by Medscape Medical News, CT screening of children with abdominal pain has skyrocketed while appendicitis rates remain unchanged, adding to growing concerns regarding the link between excessive radiation exposure and cancer risk later in life.

"Broadly-applicable strategies to systematically maximize diagnostic accuracy for childhood appendicitis, while minimizing ionizing radiation exposure, are urgently needed," the authors write, noting that evaluations may be streamlined by using algorithms developed with broad validity to decrease reliance on preoperative imaging and radiation exposure while avoiding unnecessary hospital transfers, admissions, operations, and missed diagnoses.

The retrospective study was published online December 24 in Pediatrics.

Community Hospitals: More CT Scans, Less Sensitivity

For the study, researchers reviewed the records of 423 children who had undergone surgery for presumed appendicitis. Preoperative imaging was performed in 93.4% of cases; final diagnoses included acute appendicitis (69.0%), perforated appendicitis (23.6%), and normal appendix (7.3%).

After adjusting for age, sex, race/ethnicity, body mass index, symptom duration, and white blood cell count, researchers found that children initially evaluated at a community hospital were 4.4 times more likely to have undergone a preoperative CT scan (odds ratio [OR], 4.37; 95% confidence interval [CI], 1.70 - 11.19; P = .002) and 80% less likely to have had an ultrasound performed (OR, 0.20; 95% CI, 0.07 - 0.58; P = .003) than those at a pediatric facility.

About 15.1% of children underwent both ultrasound and CT before surgery, particularly if they were girls (OR, 4.51; 95% CI, 1.47 - 13.82; P = .008) or had a lower body mass index percentile (OR, 0.98; 95% CI, 0.96 - 1.00; P = .03), longer symptom duration (OR, 1.81; 95% CI, 1.15 - 2.86; P = .01), or lower white blood cell count (OR, 0.87; 95% CI, 0.78 - 0.97; P = .01). Most children undergoing both tests had the ultrasound first (46/64, 71.9%), and normal/indeterminate results were followed up with CT (OR, 17; 95% CI, 7.7 - 37.0).

Although high overall, CT scans performed at pediatric hospitals tended to be more sensitive for any appendicitis and for perforated appendicitis than those done at community hospitals (98.8% vs 93.4% [P = .07] and 75.0% vs 49.0% [P = .045], respectively). Sensitivities were highest for older children (aged 13 - 18 years) and those not obese; insufficient numbers of underweight children were available for analysis.

Accuracy of ultrasound for diagnosing appendicitis was found to be moderate in the pediatric hospital setting (weighted κ, 0.36; 95% CI, 0.24 - 0.48) and highest among older children (aged 13 - 18 years; weighted κ, 0.38; 95% CI, 0.22 - 0.54) and boys (weighted κ, 0.40; 95% CI, 0.21 - 0.55); rarity of use in community hospitals precluded any evaluation of ultrasound sensitivity in this setting.

"Variation in diagnostic imaging use for pediatric appendicitis by initial evaluation location might stem from multiple factors, such as availability of imaging or the perceived need for diagnosis confirmation," the authors comment, noting that ultrasound may be less available in community hospitals and that emergency physicians may have low risk tolerance for pediatric diagnostic errors and malpractice claims, preferring to place their confidence in CT scans.

The study was supported by an award from the National Center for Research Resources of the National Institutes of Health and by the St. Louis Children's Hospital Foundation–Children's Surgical Sciences Institute. The authors have disclosed no relevant financial relationships.

Pediatrics. Published online December 24, 2012. Abstract