Multimodality ultrasound in Crohn's disease strictures

Stricture formation in Crohn's disease (CD) poses a significant clinical challenge, often requiring differentiation between inflammatory and fibrotic components to guide appropriate therapy.

To evaluate the utility of multimodal intestinal ultrasound - including small intestine contrast ultrasonography (SICUS), contrast-enhanced ultrasound (CEUS), and ultrasound-based elastography - in detecting and characterizing CD-related small bowel strictures.

A review was conducted in accordance with Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines. A comprehensive search of PubMed and EMBASE databases from inception to June 2025 yielded 697 records, respectively. After screening and full-text assessment, 43 studies were included. Eligible studies reported on the use of SICUS, CEUS, and elastography for detecting or phenotyping CD strictures, with comparisons to cross-sectional imaging, histopathology, endoscopy, or surgical findings.

Across heterogeneous study designs, SICUS demonstrated high sensitivity for stricture detection (typically approximately 88%-98%) with specificity that varied by cohort and criteria. Common thresholds included bowel wall thickness > 3 mm, luminal narrowing < 1 cm, and/or prestenotic dilation > 2.5 cm. CEUS effectively distinguished fibrotic from inflammatory strictures using time-intensity curve metrics: Fibrotic strictures showed reduced peak enhancement (e.g., 25 dB vs 38 dB), and lower perfusion area under the curve (AUC) values (e.g., 570 intensity time units vs 1168 intensity time units), reflecting diminished vascularity. Cutoffs such as peak enhancement < 30 dB and AUC < 700 units were associated with fibrosis. Elastography - particularly shear wave elastography achieved AUCs of 0.88-0.91 for fibrosis detection using cutoffs of 2.5-2.9 m/second (sensitivity 80%-88%, specificity 85%-100%). Strain ratio thresholds between 2.2 and 3.0 also differentiated fibrotic from inflammatory lesions with diagnostic AUCs up to 0.91. Among elastography modalities, shear wave elastography consistently outperformed strain elastography and acoustic radiation force impulse in accuracy and reproducibility.

Multimodal intestinal ultrasound - including SICUS, CEUS, and elastography - offers a comprehensive, radiation-free framework to detect, localize, and phenotype CD strictures. While performance is promising, variability in thresholds and reference standards limits generalizability. Standardized acquisition, predefined cut-offs, and multicenter validation are priorities before widespread adoption in treatment algorithms.