Inflammatory Bowel Disease Imaging, New Insights


MD, Honorary Consultant in Radiology – Senior Lecturer University of Edinburgh ,UK


Crohn’s disease (CD) is a chronic transmural inflammatory disease of the gastrointestinal tract which can be assessed by ultrasound. Unenhanced ultrasound may evaluate the localization and the length of the affected intestinal segments and may suggest the presence of mural fibrosis based on the layered appearance of the bowel wall. Contrast-enhanced ultrasound of the bowel is performed by wideband transducers including the microbubble resonance frequency. Contrast-enhanced ultrasound has become an important imaging modality in patients with CD for the grading of disease activity, the differentiation between small bowel stricture due to inflammation or mural fibrosis, and for the assessment of the response to specific pharmacologic therapy. New dedicated software packages allow the accurate quantification of the enhancement within the small bowel wall after microbubble contrast agent injection to obtain different kinetic parameters - percentage of the maximal enhancement, the time-to-the peak enhancement, and the area under the time–intensity curve - which may differentiate mural inflammation from fibrosis and responders from non-responders to the specific pharmacologic therapy. The main advantage of contrast-enhanced ultrasound in the real-time assessment of the perfusion of the bowel wall but the scan is necessarily limited to one single loop each time. US strain or shear wave elastography can be considered an additional tool to complete US assessment of the bowel wall in patients with CD. US strain elastography allows to assess the bowel wall stiffness to distinguish acute inflammation from fibrosis in patients with CD and increases the diagnostic confidence if compared to contrast-enhanced US alone.
US technique to scan small bowel
Contrast-enhanced ultrasound and microbubble contrast agents
Assessment of Crohn disease activity by contrast-enhanced ultrasound
Differentiation of mural inflammation and fibrosis by contrast-enhanced ultrasound
Quantitation of echo-signal intensity to identify responders from non-responders to therapy
Differentiation of mural inflammation and fibrosis by US strain elastography
Major strengths and weakness of contrast-enhanced US and strain elastography in comparison to the other imaging modalities