SWE of the Bowel Wall in Crohn's Disease: Differentiation of Fibrotic and Inflammatory Strictures
Clinical Challenge
In Crohn's disease (CD), the bowel wall may thicken due to either inflammatory or fibrotic processes, which have different therapeutic implications. According to EFSUMB (Săftoiu et al., 2019), elastography—compressive (SE) and shear wave (SWE)—is used for the clinical differentiation of fibrotic and inflammatory lesions in CD.
Method Principle
SWE (shear wave elastography) is a non-invasive method for measuring tissue stiffness. Focused acoustic impulses cause microscopic tissue displacement, inducing perpendicular shear waves, the propagation speed of which is tracked by ultrasound. Stiffer tissues demonstrate increased shear wave speed (Hagen-Ansert, 2023).
Differentiation of Strictures
According to EFSUMB section 9.3.1 "Distinction between fibrous and inflammatory strictures in Crohn's disease": several studies on animal models and human specimens conclude that stiffness is associated with the presence of fibrotic strictures. Thus, increased wall stiffness indicates a fibrotic component, whereas inflammatory thickening is characterized by lower stiffness.
The method of US-based real-time elastography for detecting fibrotic bowel tissue in stenosing CD is described in the work by Baumgart DC et al. (Radiology, 2015), cited in the abdominal ultrasound guide (Kamaya et al., 2022).
Limitations
According to EFSUMB (Săftoiu et al., 2019), artifacts complicate strain visualization and make targeted SWE or SE measurement more challenging and operator-dependent. Specific numerical stiffness thresholds for distinguishing fibrotic and inflammatory strictures in the provided fragments are absent [clarify].
Role in Comprehensive Assessment
Elastography is considered part of a multiparametric assessment of the bowel. Within the GIUS (Maconi et al., EFSUMB, 2018) and CEUS approaches (Sidhu et al., 2018; Nylund et al., 2013), quantitative assessment is also used to compare inflammatory and fibrotic lesions in CD.
Frequently asked questions
What does increased bowel wall stiffness indicate in SWE for a patient with CD?
According to EFSUMB, increased stiffness is associated with the presence of a fibrotic stricture; studies on animal models and human specimens confirm this association.
What are the threshold values of stiffness that differentiate fibrosis from inflammation?
Specific numerical thresholds are not provided in the fragments [clarify].
What elastography methods are used in CD?
According to EFSUMB (Săftoiu et al., 2019), compressive elastography (SE) and shear wave elastography (SWE) are used.
What are the main limitations of the method?
Artifacts complicate strain visualization, making targeted SWE/SE measurement more challenging and operator-dependent (EFSUMB, 2019).
Is elastography used in isolation?
No, the method is considered within the framework of comprehensive bowel assessment (GIUS, CEUS), including the comparison of inflammatory and fibrotic lesions.