Intestinal ultrasonography in adults with Crohn's disease: a 2020 update.

In the last years intestinal ultrasonography (IUS) has increased its role in the management of inflammatory bowel diseases (IBD), that include Crohn's disease (CD) and ulcerative colitis. This is due to the fact that IUS is a non-invasive, inexpensive, and well-tolerated examination technique. Furthermore, it allows a real-time diagnosis with no radiation exposure. Usually, convex and linear probes with frequency between 3.5 and 12 MHz are used, also with the Color- Power Doppler. Focusing on CD, the IUS images of clinical interest are: bowel wall thickening (greater than 3 mm), pseudostratification and the wall vascularization. Moreover, IUS demonstrates inflammatory mass, loss of colonic haustration and the complications of the disease, such as stenosis, abscesses, and fistulas as well as other extraintestinal manifestations, such as lymph node enlargement and changes in the appearance of the mesenteric adipose tissue (creeping fat). Oral and intravenous contrast are used to obtain a better visualization of the bowel wall and to increase the diagnostic accuracy of IUS. In particular, intravenous contrast, administered during the procedure, allows to differentiate between active disease (bowel wall enhancement) and the fibrostenotic complications. Contrast-enhanced ultrasonography (CEUS) was proven to be useful in the follow-up and the disease recurrence detection. Beyond the support in the initial diagnosis, IUS has an important role in the follow-up of patients with CD, to monitor the response to the medical therapy and to detect possible complications. Furthermore, it can predict the recurrences after surgery, with more accuracy if Color-Doppler is used.