Transrectal Endoscopic Ultrasound (TRUS) Elastography in Inflammatory Bowel Disease (IBD)

Abstract

Background and Aims: Establishing the diagnosis of Crohn's disease (MC) or ulcerative colitis (UC) sometimes is very difficult. When IBD is confined to the colon, there is a lack of diagnostic tools for distinction between Crohn's colitis and ulcerative colitis, which is especially important in the definitive phenotyping before surgical decision. The aim of this study was to assess the potential role of the TRUS elastography in distinction between MC and UC. The idea is based upon the fact that MC is transmural disease, and UC is limited to the mucosa and submucosa. These tissue characteristics are reflected in differences of the elasticity in rectal and perirectal tissue. Changes in the tissue elasticity can be obtained qualitatively by elastography with different coloures (from red-soft tissue to blue-hard tissue) or quantitatively using strain ratio score. Methods and Results: Rectal wall thickness and elastomode of patients were measured by TRUS elastography. Endoscopist was blind for patient diagnosis. SPSS ver. 17 was used for statistical analysis. In pilot study we included 31 patients; 16 patients (52%) with MC and 15 patients (48%) with UC. Average thickness of rectal wall in all study patients was 6.43 mm (± 0.47 SE). In MC group mean rectal thickness was 7.28 mm (± 0.76 SE) compared to 5.52 mm (± 0.44 SE) in UC group. There was no statistical significant difference between MC and UC groups in perirectal thickness (t=1.97, df=29, p=0.058). Perirectal elastomode showed statistically significant difference between this two groups (χ2=18.6, df=2, P<0,001). Twelve (75%) patients in MC group had hard elastomode compared to none of patients in UC group, meaning that hard elastogram had positive predictive value of 100% for patients with MC. We also evaluated strain ratio (SR) of rectal tissue. Strain ratio is ratio of strain between two regions of interest (ROI) in the same image. Mucosal tissue was used as first ROI and perirectal tissue as second. SR was measured 3 times and middle value was used in statistical analysis. Sixteen patients were included in our study; 7 (44%) with MC and 9 (56%) with UC. Mean value of SR was higher in MC group (1.07 ± 0.26) then in UC group (0.26 ± 0.21). This difference was statistically significant (t=6.85, df=14, p<0.001). Conclusion: TRUS elastography provides a valuable information regarding the stiffness of the rectal and perirectal tissue, and can help to differentiate MC from UC. This is a promising new diagnostic tool in the field of IBD. Our study is ongoing and we expect improvement of the method, with increasing number of patients.