Computed tomography and magnetic resonance imaging in the diagnosis of the small and large intestine strictures in Crohn’s disease. Radiological semiotics and assessment of the inflammation activity

Rationale: Crohn's disease is characterized by continuous severe course, and in a half of the patients is associated with formation of strictures that are difcult to treat and significantly decrease quality of life. Difficulties during the differentiation between inflammation-related and fbrostenotic strictures and divergent approaches to their treatment in patients with Crohn's disease indicate the need in precise diagnostics and systematization of the radiological semiotics of strictures.

Aim: To propose radiological semiotics of the small and large intestine strictures based on the results of multiaxial computed tomography (MACT) and magnetic resonance imaging (MRI).

Materials and methods: MACT and MRI visualization was performed in 40 patients with a stenotic type of Crohn's disease.

Results: The radiological signs of the strictures were classifed into two main groups: intestinal and extra-intestinal. They were systematized according to nine criteria, such as character of formation, etiology, number, inflammation grade, extension, shape, and location, presence of ileus and presence of other complications. The inflammation activity in the intestinal wall was evaluated during the postcontrast assessment: active inflammation in the arterial phase (at 25 seconds after administration of the contrast agent), chronic inflammation in the delayed phase (at 10 minutes). The MRI results were cross-checked with those of MACT. At the precontrast stage, MRI was more informative as per the width of the intestinal lumen, whereas MACT was preferential in the diagnosis of fat infltration of the intestinal wall. Post-contrast MACT and MRI were diagnostically equivalent. The most indicative for active inflammation were diffuse weighed MRI images, arterial phase MACT and MRI, whereas chronic inflammation and wall fbrosis were better diagnosed at the delayed phase (at 10 minutes) of MACT and MRI. Both methods (MACT and MRI) could not differentiate between the submucous and muscular layers of the intestinal wall. Mixed type of inflammation was seen in the walls of intestinal strictures: chronic inflammation dominated in the intermediate, most extensive part of a stricture and remained stable during the dynamic follow-up, whereas active inflammation was found in the marginal parts of the strictures, which were most susceptible to changes during the follow-up.

Conclusion: Based on a set of certain signs obtained by radiological visualization, we propose a registry for stricture assessment based on evaluation of the inflammation activity.