Background and aims: Transmural disease assessment in small bowel Crohn's disease (CD) is usually done by cross-sectional imaging (computed tomography/Magnetic resonance enterography: CTE/MRE). However repeated testing can be cumbersome, costly and may involve radiation (CTE). Small intestinal contrast ultrasonography (SICUS) used as a triage test might allow to avoid repeated cross-sectional imaging for monitoring small bowel CD and help take accurate clinical decisions.
Methods: We did this prospective, paired, confirmatory study (CACTUS-CD:NCT06125678) to test accuracy of SICUS against reference test (cross-sectional imaging: CTE/MRE) in known small bowel CD. SICUS was done in the same day morning prior to scheduled CTE/MRE . Radiologists reporting CTE/MRE were blinded to SICUS report. Change in management decision after CTE/MRE over SICUS, the correlation between CTE/MRE and SICUS for maximum wall thickness/length/extent of involved small bowe and complications (stricture, fistula and abscess) were evaluated.
Results: Total 96 patients (median age 37 years, range: 18-67years, 69% male) with small bowel CD underwent SICUS prior to CTE (n=57)/MRE (n=39) between July to November 2023. SICUS had very strong and strong correlation with cross-sectional imaging with regard to maximum bowel wall thickness (BWT) of involved small bowel (Spearman’s R=0.84, p<0.001) [correlation equation: BWT (IUS)=0.68 +0.92 x BWT (cross sectional imaging)] and length of small bowel involved (R=0.71, p<0.001) [correlation equation: length (IUS)=0.9 +0.47 x length (cross-sectional imaging)] respectively (figure 1). Agreement of SICUS and cross-sectional imaging with regard to extent and identification of i multi-focal involvement wre 78% and 72% respectively. The accuracy of SICUS to detect CD complications were 78% (strictures), 94% (intra-abdominal fistula) and 96% (intra-abdominal abscess) respectively considering cross-sectional imaging as gold standard (Figure 2). Majority of the missed lesions on SICUS were in the proximal small bowel. Inspite of wide variation in several parameters, the overall management decision after SICUS remained unaltered even after CTE/MRE in 81% (n=78) (figure 2). CTE/MRE changed management decision in only 19% (n=18).
Conclusion: SICUS can correctly identify activity, extent and complications of small bowel disease in known CD in the majority with minimal incremental yield of cross-sectional imaging in changing clinical management decisions. Cross-sectional imaging over and above SICUS could be helpful for detecting proximal small bowel involvement (Clinicaltrials.gov: NCT06125678).

Uday Kumar Marri

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