US Elastography-derived Shear Wave Velocity Helps Distinguish Acutely Inflamed from Fibrotic Bowel in a Crohn Disease Animal Model

Purpose: To determine if acoustic radiation force impulse elastography- derived bowel wall shear wave velocity (SWV) allows distinction of acutely inflamed from fibrotic intestine in a Crohn disease animal model. Materials and Methods: University Committee on the Use and Care of Animals approval was obtained. An acute inflammation Crohn disease model was produced by treating eight Lewis rats with a single administration of trinitrobenzenesulfonic acid (TNBS) enema, with imaging performed 2 days later in the surviving six rats. Colonic fibrosis in an additional eight Lewis rats was achieved by administering repeated TNBS enemas during 4 weeks, with imaging performed in the surviving seven rats 7 days later to allow acute inflammation resolution. Nine transcutaneous bowel wall SWV measurements were obtained from the colon in all rats without and with applied strain. Mean SWVs without and with applied strain were compared between animal cohorts by using the Student t test, and receiver operating characteristic (ROC) curves were created to assess diagnostic performance. Results: Mean bowel wall SWVs were significantly higher for fibrotic versus acute inflammation cohort of rats at 0% (3.4 +/- 1.1 vs 2.3 +/- 0.5 m/sec; P =.047) and 30% (6.3 +/- 2.2 vs 3.6 +/- 0.9 m/sec; P = .02) applied strain. Both acute inflammation and fibrotic cohort of rats demonstrated linear increases in mean SWV with increasing applied strain, with significantly different mean slopes (P = .02) and y- intercepts (P = .02). The area under the ROC curve of the SWV ratio (mean SWV/applied strain) for differentiating histopathologically confirmed fibrotic from inflamed bowel was 0.971. Conclusion: Bowel wall SWV helps distinguish acutely inflamed from fibrotic intestine in a Crohn disease animal model.