Possibilities of transrectal ultrasound examination in assessing the severity and differential diagnosis of inflammatory bowel disease: a comparative analysis in ulcerative colitis and Crohn’s disease

Background. Colonoscopy with biopsy remains the gold standard for the diagnosis of inflammatory bowel disease (IBD). However, this method has a number of limitations, especially in severe clinical conditions. In this regard, there is a growing need for less invasive imaging methods. One of these methods is transrectal ultrasound (TRUSD), which provides high-resolution imaging of the wall of the rectum and distal sigmoid colon. TRUSD allows for quantitative assessment of the intestinal wall thickness, stratification of its layers, detection of hypervascularisation characteristic of active inflammation, as well as identification of infiltrative and fibrotic changes. The data of modern clinical trials demonstrate the high sensitivity and specificity of this method, which makes it advisable to use TRUSD more widely in clinical practice. Despite its numerous advantages, TRUSD remains an underutilised method in clinical practice, although it is a promising non-invasive tool for the diagnosis and monitoring of patients with IBD. The aim of the study was to analyse the possibilities and clinical effectiveness of transrectal ultrasound in the diagnosis of ulcerative colitis (UC) and Crohn’s disease (CD). Materials and methods. TRUSD was performed on an expert-class ultrasound scanner SonoScape S60 using a 3.5 MHz low-frequency convection transducer and a 6 MHz recto-vaginal convection transducer. Transperineal and trans­rectal approaches were used. Results. Thickening of the rectal wall > 5 mm was typical for 100 % of patients. The wall thickness was significantly lower in patients with CD compared to those with UC — (5.99 ± 0.42) mm vs. (7.12 ± 0.20) mm, respectively (p = 0.01). The thickness of the mucosal layer in UC was 1.8 times higher than in CD (p = 0.05), and the thickness of the submucosal layer was 1.3 times higher (p = 0.01). On the contrary, the thickness of the muscular layer in patients with CD was significantly higher than in those with UC — (1.69 ± 0.21) mm vs. (1.17 ± 0.04) mm (p = 0.05). The wall thickness ((6.80 ± 0.21) mm vs. (8.15 ± 0.42) mm, p = 0.04) and submucosal layer thickness ((4.14 ± 0.21) mm vs. (5.28 ± 0.28) mm, p = 0.008) significantly differed between moderate and severe UC. Almost 86.7 % of the examined patients with severe UC had grade 3 blood flow density in the rectal wall, whereas in moderate UC, 61.5 % of patients had grade 1. When performing elastometry of the intestinal wall, there was a tendency to increase the strain coefficient in patients with CD compared to UC. The ROC analysis allowed us to establish the high quality of the diagnostic indicator — the thickness of the muscular layer — for the differential diagnosis of UC and CD. High diagnostic value was also obtained for the thickness of the submucosal layer in assessing the severity of UC. Conclusions. TRUSD is an effective non-invasive method for evaluating inflammatory bowel diseases. Doppler scanning allows to assess the degree of vascularisation of the intestinal wall, which correlates with the clinical activity of IBD. Intestinal wall elastometry is useful in determining the severity of inflammation. The thickness of the intestinal wall and submucosa have a high prognostic value in detecting severe UC. A muscular layer thickness of 1.3 mm can be used as an auxiliary criterion for the differential diagnosis between UC and CD.