Prospective evaluation of high-frequency mini-probe ultrasound colonoscopic imaging in ulcerative colitis: a valid tool for predicting clinical severity

BACKGROUND: High-frequency mini-probe ultrasound imaging permits trans-mural cross-sectional imaging of the colorectal wall. In ulcerative colitis, prognosis is dependent on the severity of mucosal inflammatory change where accurate assessment of disease activity is required to optimize medical therapy. Furthermore, predicting relapse of disease using conventional endoscopic, histopathological and clinical criteria has not proven reliable. AIM: To evaluate the correlation of high-frequency mini-probe imaging with standardized measures of clinical, endoscopic and histopathological severity. METHODS: High-frequency ultrasound images were obtained from the caecum to rectum in 200 patients. Tsuga colorectal ultrasound criteria were then compared to the endoscopic Baron score, Seo activity score and Matts histopathological grade. RESULTS: For rectal disease, the kappa coefficient between Tsuga criteria I/II and Matts grade 1/2 was 0.78 (95% CI, 0.67-0.89), 0.57 (95% CI, 0.46-0.68) and 0.48 (95% CI, 0.34-0.62) for Tsuga class IIIa/b, IVa/b and Matts grade 3a/b and 4, respectively. Colonic imaging showed a kappa coefficient between Tsuga class I/II and Matts grade1/2 of 0.76 (95% CI, 0.72-0.8). Tsuga class IIIa-IIIb/IVa-IVb as compared to Matts grade 3a-3b/4 yielded kappa coefficients of 0.49 (95% CI, 0.43-0.55) and 0.62 (95% CI, 0.56-0.69), respectively. In the rectum both the total wall thickness, mucosa and submucosa were significantly thicker in Matts grade 3b and 4 disease as compared to Matts grade 1/2 (P < 0.02) for all parameters. A significant increase in colonic total wall thickness was observed between Matts score 4 and Tsuga grade 1-3a disease (P < 0.001). CONCLUSIONS: High-frequency ultrasound is a valid adjunctive 'tool' for the trans-mural assessment of the colorectal wall in ulcerative colitis. This technique may aid in the initial diagnosis, and ongoing chronic management of disease.