Contrast-enhanced US in Crohns disease

Abstract

The diagnostic potential of ultrasound in the assessment of Crohn's disease is enormous. Ultrasonography is not only a method for radiologists, but also a clinical tool that can be applied to evaluate the patient bedside. The GI wall is most often visualized as a layered structure normally consisting of 5 layers. When examining the intestines, it is preferable to use frequencies above 7.5 MHz to enable optimal resolution and visualisation of wall layers, thickened bowel walls and target lesions. Disease activity in Crohn's disease using bowel wall thickness and Doppler measurements as a marker of inflammation can also be obtained by ultrasound. By adding CEUS, enhancement in different wall layers can be evaluated and quantified in Crohn's disease and this correlates to clinical activity index (CDAI) with good sensitivity and specificity. Quantitative measurements of bowel enhancement obtained by CEUS also correlate with severity grade determined at endoscopy. In patients with a stricture of the bowel and resultant bowel obstruction, it is important to determine if there is active inflammation at the site of stricture or if the obstructed segment is fibrotic. Preliminary studies indicate that CEUS appears to be useful in the recognition of a stenosis in patients with Crohn's disease. Using CEUS, the active inflammatory components will enhance whereas the fibrotic stricture will enhance less. Distinguishing abscesses from inflammatory infiltrates is an important clinical task in the management of Crohn's disease. If the tissue close to an affected bowel loop is completely devoid of microbubble signals, most likely this lesion represents avascular abscesses rather than inflammatory infiltrates. In the upcoming update of EFSUMB guidelines on CEUS, new indications are monitoring of treatment response and follow-up of transplanted patients. In conclusion, CEUS is a useful clinical tool in the management of patients with Crohn's disease, particularly to look for abscesses and evaluate stenotic segments.