Assessment of Crohn’s disease-associated small bowel strictures and fibrosis on cross-sectional imaging: a systematic review

Abstract

Patients with Crohn’s disease commonly develop ileal and less commonly colonic strictures, containing various degrees of inflammation and fibrosis. While predominantly inflammatory strictures may benefit from a medical anti-inflammatory treatment, predominantly fibrotic strictures currently require endoscopic balloon dilation or surgery. Therefore, differentiation of the main components of a stricturing lesion is key for defining the therapeutic management. The role of endoscopy to diagnose the nature of strictures is limited by the superficial inspection of the intestinal mucosa, the lack of depth of mucosal biopsies and by the risk of sampling error due to a heterogeneous distribution of inflammation and fibrosis within a stricturing lesion. These limitations may be in part overcome by cross-sectional imaging techniques such as ultrasound, CT and MRI, allowing for a full thickness evaluation of the bowel wall and associated abnormalities. This systematic literature review provides a comprehensive summary of currently used radiologic definitions of strictures. It discusses, by assessing only manuscripts with histopathology as a gold standard, the accuracy for diagnosis of the respective modalities as well as their capability to characterise strictures in terms of inflammation and fibrosis. Definitions for strictures on cross-sectional imaging are heterogeneous; however, accuracy for stricture diagnosis is very high. Although conventional cross-sectional imaging techniques have been reported to distinguish inflammation from fibrosis and grade their severity, they are not sufficiently accurate for use in routine clinical practice. Finally, we present recent consensus recommendations and highlight experimental techniques that may overcome the limitations of current technologies.

Human Intestinal Mononuclear Phagocytes in Health and Inflammatory Bowel Disease

“…In UC patients, the degree of fibrosis is proportional to the degree of inflammation, even if the fibrosis-associated strictures are less prevalent than in Crohn's patients (294). Despite the problem of fibrosis in IBD (295,296), the mechanism by which Mfs contribute to fibrosis-associated pathology is poorly understood. Several Crohn's-associated susceptibility loci, including some related to MNP-associated inflammation such as NOD2, ATG16L1, IL-12B, IL-23R, and CX3CR1, are predictors of fibrostenosis (294).…”

Fibrostenotic strictures in Crohn’s disease

“…A bowel stiffness ratio ≥ 2 in patients with CD could predict anti-TNF therapy failure and surgery. 112,122 CTE is superior to MRE with the advantages of higher resolution, rapid diagnosis, lower cost, and wider availability but requires radiation exposure. 107 CTE findings of strictures including luminal narrowing and wall thickening in the absence of intestinal wall inflammation such as mucosal hyperenhancement (including mural stratification), mesenteric hypervascularity (the so-called comb sign), and mesenteric fat stranding are presumed to indicate a fibrotic stricture.…”

Differentiation of fibrotic and inflammatory component of Crohn’s disease-associated strictures

“…2) promise to improve the quantification of bowel wall fibrosis. 20 Table 1 summarizes the main characteristics of novel imaging modalities that had been investigated to detect and quantify fibrosis in CD, whereas Table 2 provides the evidence obtained in studies testing the techniques against histopathology. [9][10][11][13][14][15][21][22][23][24][25] To date, all the evidence comes from single-center studies with relatively small samples.…”