Background
European Federation of Societies for Ultrasound in Medicine and Biology has suggested contrast-enhanced ultrasound (US) of the bowel wall as an alternative imaging modality for the follow up of children with Crohn disease. However, the level of evidence is based on adult patients. The purpose of our study was to evaluate the diagnostic performance of contrast-enhanced US in the estimation of Crohn disease activity in children. Alongside, we evaluated its’ potential role in clinical practice by comparing it with established methods: ileocolonoscopy, ultrasound with colour Doppler imaging (US-CDI), Pediatric Crohn disease activity (PCDAI), calprotectin and magnetic resonance enterography (MRE). The second purpose of our study was to establish the role of contrast-enhanced US in the estimation of therapeutic response.
Methods and patients
Thirty-six patients (age 3,5-18) with exacerbation of Crohn disease were included in this prospective study. In the first part of the study, disease activity was evaluated in 24 children on 40 bowel segments using US-CDI and subjective and quantitative contrast-enhanced US. Quantitative contrast-enhanced US parameters were compared to histopathology results and provided us with cut off values for different grades of CD activity, required for future evaluation. Ileocolonoscopy was used as the reference standard when calculating the diagnostic accuracy of CD activity evaluation with quantitative contrast-enhanced US and already established methods: PCDAI, calprotectin, ileocolonoscopy (36 children) and MRE (19 children). Therapeutic response was evaluated with quantitative contrast-enhanced US and PCDAI as the reference standard in 11 children, in which pharmacological treatment was newly introduced or changed. Persistent thickening of bowel wall was required on control US-CDI in all subjects. Treatment choice and follow up period were defined by the paediatrician.
Results
The peak enhancement value (PE) was the most predictive parameter of CD activity at quantitative contrast-enhanced US evaluation. PE with the cut off 6,9 had 72,2% sensitivity and 100% specificity in prediction of a moderate or severe grade of inflammation at histopathology. Four segments were falsely evaluated as negative, possibly due to the presence of fibrosis in combination with mixed inflammation (moderate chronic and acute inflammation of different degrees) observed at histopathology of these segments.
Compared to subjective contrast-enhanced US and US-CDI, quantitative contrast-enhanced US also had the highest diagnostic accuracy of 87,5% (subjective contrast-enhanced US 77,5%, US-CDI 72,5%). In detecting active CD at ileocolonoscopy the quantitative contrast-enhanced US had 78,6% sensitivity (PCDAI 89%, calprotectin 92%) and 100% specificity (PCDAI 75%, calprotectin 43%). The quantitative contrast-enhanced US had a moderate correlation and high agreement with the ileocolonoscopy. MRE had lower specificity compared to quantitative contrast-enhanced US (MRE 67%, quantitative contrast-enhanced US 100%), but higher sensitivity (MRE 100%, quantitative contrast-enhanced US 75%) and diagnostic accuracy (MRE 94,7%, quantitative contrast-enhanced US 79%). Diagnostic accuracy of quantitative contrast-enhanced US in the estimation of therapeutic response was 72,7 %.
Conclusion
Quantitative contrast-enhanced US has the potential of becoming a complementary method in the evaluation of disease activity and therapeutic response of CD in children. Fibrosis may affect peak enhancement results and underestimate inflammatory activity.
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