In this cohort of children operatively treated for presumed appendicitis at a single, tertiary-care children’s hospital, the majority underwent preoperative imaging. Diagnostic imaging selection and accuracy varied with the site of initial evaluation. Controlling for factors potentially associated with referral bias and illness severity, the performance of preoperative abdominal-pelvic CT scan was significantly associated with initial evaluation at community hospitals, whereas abdominal ultrasound was more likely obtained with initial evaluation at the children’s hospital. Variation in CT use by hospital type has been reported,20,21
and, here, we extend the observation by examining ultrasound in combination with CT use and adjusting for subject characteristics that potentially influenced the likelihood of interfacility transfer. In addition, we found that CT and ultrasound studies performed at community hospitals in comparison with the children’s hospital had diminished accuracy for diagnosing appendicitis.
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. First, compared with ultrasound, the ready availability of CT scans may account for frequent use in community hospitals. CT use for pediatric abdominal pain evaluation has markedly increased over the past decade in emergency departments, particularly nonpediatric-focused departments.15,16
By contrast, ultrasound use over time has remained constant16
; decreased or inconsistent availability of emergent ultrasound within community hospitals might contribute to this pattern.10,11
Second, concern over diagnostic errors might prompt CT use. Appendicitis is among the leading diagnoses associated with pediatric diagnostic errors22
and malpractice claims.23
Low physician risk tolerance among emergency medicine physicians has been associated with more frequent CT use for evaluation of adult acute abdominal pain.24
Finally, practitioners might have greater confidence in CT scans in comparison with ultrasound; a previous survey of North American pediatric surgeons in 2004 demonstrated preference for CT over ultrasound in appendicitis evaluation.25
However, our finding of more frequent ultrasound use in the children’s hospital may reflect conscious avoidance of ionizing radiation exposure. Interestingly, subjects who had both CT scan and ultrasound were more likely to be female and to have lower BMI percentile, longer duration of symptoms, and lower WBC count. Ultrasound may have served to evaluate for gynecologic pathology in girls. The longer duration of symptoms might have increased the perceived urgency to establish the diagnosis of appendicitis, although lower WBC count would not be expected with advanced or perforated appendicitis. Rather, imaging with both CT and ultrasound might have been obtained in clinically confusing cases, the identity of which cannot be discerned in retrospect. In many instances, CT scans followed nondiagnostic ultrasound, as recommended in several previous studies.26–28
Despite frequent use, CT accuracy was reduced when performed in the community setting. Although overall CT sensitivity for any appendicitis was similar to previous reports,7
CT scans performed at the children’s hospital were somewhat more sensitive than at referring institutions. For perforated appendicitis, CT studies from the children’s hospital had significantly higher sensitivity. One potential reason for diminished accuracy is that multidetector CT, which is used at the children’s hospital, might be less available at referring community hospitals. Multidetector CT offers the advantages of improved resolution through thinner sections and coronal reconstructions that could enable visualization of the appendix.29
Lack of intravenous contrast,30
suboptimal intravenous contrast bolus timing, and patient movement, especially in younger children, may have affected the quality of CT scans performed at referring hospitals in comparison with the children’s hospital. Finally, the interpretation of CT by general versus pediatric radiologists may contribute to the CT accuracy difference.31
Technical quality of imaging and radiologist type were not specifically captured in this study.
In contrast to CT scan sensitivity, ultrasound sensitivity for appendicitis was much lower than previously reported in a meta-analysis.7
Ultrasounds performed at community hospitals were less sensitive for the detection of appendicitis and perforation. Although children evaluated at the children’s hospital frequently underwent ultrasound alone, fair to moderate accuracy combined with a low negative appendectomy rate implies that clinical impression, derived from symptoms, physical examination findings, and laboratory results, influenced clinical decision-making when ultrasound findings were not definitive. Evaluation by a pediatric surgeon has been previously shown to have comparable accuracy to imaging studies in the assessment of children for appendicitis.32
However, evaluation by a pediatric surgeon often necessitates transfer to a tertiary-care or children’s hospital.
Patient-specific factors impacted both CT and ultrasound accuracy. Trends toward diminished CT accuracy were associated with younger patient age, obesity, and male gender, although κ was not significantly different, possibly because of the small numbers of studies. For ultrasound, κ trended lower in younger and female children. Previous studies have examined the impact of obesity on ultrasound and CT accuracy. For ultrasound, Butler et al33
found a decreased likelihood of visualizing the appendix with increased abdominal wall thickness and retrocecal appendix location, and Schuh et al34
found diminished accuracy for appendicitis in children who were obese in comparison with children who were lean. Abo et al9
identified a trend toward decreased ultrasound sensitivity in overweight and obese children, but no difference in CT sensitivity. In this cohort, ultrasound sensitivity for any appendicitis was not affected by obesity; however, few obese children had ultrasound, possibly because of low confidence in the diagnostic utility of ultrasound for these children. Girls had significantly lower ultrasound sensitivity for any appendicitis compared with boys. This gender difference might reflect the use of ultrasound to exclude gynecologic causes of abdominal pain rather than to diagnose appendicitis.
To reduce reliance on CT scans, diagnostic algorithms and clinical scoring systems have been developed.35–39
Most of these were validated in children’s hospitals, and differing thresholds for imaging and operation were found even with the same scoring system.35,36
Unfortunately, both symptoms and physical examination assessment have low correlation among practitioners,40,41
which could account for the variable cut points. To address CT use within community hospitals, clinical decision tools are needed that are applicable to practitioners with varying levels of pediatric or surgical expertise at all points of evaluation. The identification of children likely to have appendicitis (high pretest probability) would potentially avoid CT scans before transfer to a center for operative treatment, while also limiting unnecessary transfers. Assessment of the reasons for obtaining CT would inform how to best reduce CT use. Optimal imaging may depend on multiple factors, such as patient age, gender, body habitus, symptoms, potential alternate diagnoses, accuracy of imaging modality for patient subtype, and specific hospital resources. The value of diagnostic confirmation in avoiding unnecessary interfacility transfer, hospital admission, operations, and treatment delays must be balanced against the harm of radiation exposure from CT, and costs to maintain ultrasound technical proficiency and to provide pediatric expertise.
The retrospective and single-center study structure presents several limitations. Additional similar analyses in other sites will ascertain the generalizability of our findings. We cannot address what specific impact imaging had in the evaluation of children with possible appendicitis; the value of normal imaging in preventing an unnecessary operation or hospital transfer could not be assessed with this cohort. The initial symptoms and physical examination findings of subjects were not recorded with sufficient consistency to permit a detailed analysis of imaging utilization with regard to clinical presentation. Consequently, the few subjects who did not have imaging during initial evaluation may have had more obvious clinical evidence of appendicitis. Nonetheless, the high imaging utilization implies that at least some CT scans and ultrasounds were confirmatory rather than essential. The selection criteria for the cohort were chosen to capture negative appendectomies; despite this, the proportion of operations performed for a normal appendix may be underestimated if the appendix was not removed. Whether community physiciansobtain imaging in children with suspected appendicitis routinely or selectively to confirm the diagnosis before interfacility transfer for operative care cannot be determined from this study. Finally, the limited number of subjects within subgroups precluded multivariable analysis of CT and ultrasound accuracy.