Comparison of MRI appendix biometrics in children with and without acute appendicitis

Identification of children with a nondiagnostic ultrasound at a low appendicitis risk using a pediatric Appendicitis Risk Calculator

OBJECTIVES

Up to 50% of ultrasounds (USs) for suspected pediatric appendicitis are nondiagnostic. While the validated low-risk clinical pediatric Appendicitis Risk Calculator (pARC) score < 15% and the low-risk US with nonvisualized appendix and no periappendiceal inflammation carry relatively low appendicitis risks, the contribution of the combination of both characteristics to this risk has never been assessed. The primary objective was to determine the proportion of children with the low-risk US-low-risk pARC combination with appendicitis. We hypothesized that this proportion would be 2.5% (upper 95% CI ≤ 5%).

METHODS

A retrospective cohort study of 448 previously healthy children 4-17 years old at a pediatric ED with suspected appendicitis, nondiagnostic US, and persistent clinical concern about appendicitis. Two investigators abstracted demographic, clinical, and imaging data. Based on published criteria, USs were classified as low-risk or high-risk. The pARC includes seven demographic, clinical, and laboratory variables and is quantified according to the published formula. The primary outcome was appendicitis, based on the histological evidence. All nonoperated patients underwent a 1-month-follow-up to exclude delayed appendicitis diagnoses.

RESULTS

Sixty of the 448 (13.4%) patients had appendicitis; 269 (60%) had low-risk US, 262 (58.4%) had low-risk pARC, and 163 (36.4%) had both characteristics. The appendicitis rates with low-risk pARC alone and low-risk US alone were 14/262 (5.4%) and 21/269 (7.8%), respectively. A total of 2/163 children (1.2%) with low-risk pARC and low-risk US had appendicitis (95% CI 0%-4.4%). Higher-risk US increased the appendicitis odds 5 (95% CI 1.54-20.55) to 11 times (95% CI 2.41-51.10) across pARC levels. The low-risk combination had sensitivity of 96.7% (95% CI 88.5%-99.6%), specificity of 41.5%, positive predictive value of 20.4%, and negative predictive value of 98.8% (95% CI 95.6%-99.9%).

CONCLUSIONS

The children with low-risk pARC and low-risk US combination are unlikely to have appendicitis and can be discharged home. The presence of higher-risk US-pARC score combinations substantially increases the appendicitis risk and warrants reassessment or interval imaging.

2024 Clinical Practice Guideline Update by the Infectious Diseases Society of America on Complicated Intra-abdominal Infections: Diagnostic Imaging of Suspected Acute Appendicitis in Adults, Children, and Pregnant People

This paper is part of a clinical practice guideline update on the risk assessment, diagnostic imaging, and microbiological evaluation of complicated intra-abdominal infections in adults, children, and pregnant people, developed by the Infectious Diseases Society of America (IDSA). In this paper, the panel provides recommendations for diagnostic imaging of suspected acute appendicitis. The panel's recommendations are based on evidence derived from systematic literature reviews and adhere to a standardized methodology for rating the certainty of evidence and strength of recommendation according to the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) approach.

Properties of ultrasound-rapid MRI clinical diagnostic pathway in suspected pediatric appendicitis-A prospective cohort study

OBJECTIVE

to determine diagnostic accuracy of an US-MRI clinical diagnostic pathway to detect appendicitis in the emergency department (ED).

STUDY DESIGN

prospective cohort study of 624 previously healthy children 4-17 years old undergoing US for suspected appendicitis and clinical re-assessment. Children with non-diagnostic USs and persistent appendicitis concern/conclusive US-reassessment discrepancies underwent ultra-rapid MRI (US-MRI pathway), interpreted as positive, negative or non-diagnostic. Cases with missed appendicitis, negative appendectomies, and CT utilization were considered clinically diagnostically inaccurate. Primary outcome was the proportion of accurate diagnoses of appendicitis/lack thereof by the pathway.

RESULTS

150/624 (24%) children had appendicitis;255 USs (40.9%) were non-diagnostic. Of 139 US-MRI pathway children (after 117 non-diagnostic and 22 conclusive USs), 137 [98.6%; 95% CI 0.96-1.00] had clinically accurate outcomes (1 CT, 1 negative appendectomy): sensitivity 18/18 [100%], specificity 119/121 [98.3%], positive predictive value 18/20 [90.5%], negative predictive value 119/119 [100%]. MRI imaging accuracy was 134/139 (96.4%); 3 MRIs were non-diagnostic (no appendicitis). In the overall algorithm, 616/624 [98.7% (0.97-0.99)] patients had accurate outcomes: 147/150 (98.0%) appendicitis cases had confirmatory surgeries (3 CTs) and 469/474 (98.9%) appendicitis-negative children had no surgery/CT.

CONCLUSION

this study demonstrated high clinical accuracy of the US-rapid-MRI pathway in suspected pediatric appendicitis after non-diagnostic US.