Intestinal ultrasound (IUS) is one of the major diagnostic tools for Crohn’s disease (CD). Above all, bowel wall thickness (BWT), which is generally considered normal if less than 3 mm, is crucial. Besides that, bowel wall stratification, presence of Doppler signal, extension of the thickened tract, mesenteric thickening, and lymph nodes are essential to the ultrasound evaluation. Particularly, a normal bowel wall presents five layers: the hyperechoic interface between the mucosa and the intestinal lumen, the hypoechoic mucosal layer, the hyperechoic submucosa, the hypoechoic muscular layer, and the hyperechoic interface between the muscular layer and the serosa. However, during an active phase of CD, the stratification is not so clearly visible and can be completely lost in some cases. Another sign of active disease is bowel wall vascularisation, described by the Limberg score, from absent to exceeding bowel wall.