P0235 Intestinal Ultrasound and Its Advanced Modalities in Characterizing Strictures in Crohn's Disease

Abstract Background Crohn’s disease (CD) strictures exhibit varying levels of inflammation and chronicity. Treatment decisions are likely to improve when the predominant phenotype is known1. Intestinal ultrasound (IUS) allows transmural evaluation with potential to characterize this predominant phenotype2. Here, we evaluated whether conventional intestinal ultrasound (IUS) in combination with advanced modalities (contrast-enhanced ultrasound (CEUS) and shear-wave elastography (SWE)) is accurate in characterizing the predominant phenotype of CD strictures. Methods CD patients with a confirmed stricture at endoscopy (non-passable with the endoscope) or MRE1 were included. All patients underwent IUS prior to a small bowel segmental resection. Histology in the resection specimen was assessed in location-matched tissue sections. Following a consensus session, two pathologists blindly assessed the predominant phenotype (inflammatory (IP), chronic (CP) or mixed (MP)) in the strictures. The primary objective of the study was to find a (combination of) IUS parameter(s) to identify strictures with an IP. Results Out of 107 patients with a CD stricture, 36 were included (median IUS and surgery: 14 days). Histology revealed an inflammatory phenotype in 7/36 (20%), chronic in 16/36 (44%) and mixed in 13/36 (36%). In univariate analysis loss of wall layer stratification (WLS) (OR:7.86, p=0.029) and CEUS parameters (best performing: wash-in area under the curve (WiAUC): cut-off:38.20 dB, AUROC:0.84, p=0.011, sens:86%/spec:77%) were associated with an IP. Bowel wall thickness (BWT) (5.74 vs 7.46 mm, p=0.002) was lower and colour Doppler signal (CDS) (OR:0.14, p=0.03) and loss of WLS (OR:0.14, p=0.027) were less present in CP. The optimal BWT to determine a CP was <6.4 mm (AUROC: 0.83, p=0.001, sens/spec: 75%). SWE correlated inversely with hypervascularity (CEUS parameters [ρ=-0.36 to -0.47, all p<0.04] and CDS [ρ=-0.68, p<0.001]) but did not determine the predominant phenotype. In multivariate analysis, loss of WLS and WiAUC≥38.20 dB indicated an IP, whereas lower BWT and CDS≤2 indicated a CP. With these parameters, the Stricture Score Amsterdam (SSA) (Table 1) was constructed where a score >2 demonstrated high accuracy for an IP (AUROC:0.88, p=0.002) and a negative score (<0) high accuracy for a CP (AUROC:0.90, p<0.0001) (Figure 1). Inter-observer agreement for the score was good (ICC:0.73, p<0.0001). A combination of IUS and CEUS is accurate to differentiate between inflammatory and chronic strictures in CD. The SSA needs external validation and evaluating its potential as a diagnostic decision aid when choosing between surgical and available medical treatments. References 1.Bettenworth D, Baker ME, Fletcher JG, et al. A global consensus on the definitions, diagnosis and management of fibrostenosing small bowel Crohn’s disease in clinical practice. Nature Reviews Gastroenterology & Hepatology. 2024:1-13. 2.Bettenworth D, Bokemeyer A, Baker M, et al. Assessment of Crohn’s disease-associated small bowel strictures and fibrosis on cross-sectional imaging: a systematic review. Gut. 2019;68(6):1115-1126. Table 1: (CDS1 absent, 2:single vessel, 3:stretches wall, 4:stretches mesentery) Figure 1 Conclusion