Assessing Active Bowel Inflammation in Crohn's Disease Using Intestinal Ultrasound: Correlation With Fecal Calprotectin

Aim: To analyze the correlation between intestinal ultrasound (IUS) and serum and fecal biomarkers, and the characteristics of small bowel disease, for the assessment of active bowel inflammation. Methods: Patients with Crohn's disease (CD) who underwent an initial IUS examination between July 2018 and November 2022 at our institution were included retrospectively. We divided small and large bowels into seven segments, and recorded the presence of active inflammation according to following criteria: bowel wall thickness ≥ mm with ≥1 of feature of active disease on IUS. The correlations between IUS-assessed activity and serum C-reactive protein (CRP, mg/dL) and fecal calprotectin (FC, μg/g) levels were analyzed. Results: A total of 127 patients were included (mean age: 32.42 ± 12.07, M:F = 90:37, median disease duration 6 years [0–35]). Of them, 78 showed active bowel inflammation (61.4%), with inflammation distal to the terminal ileum being the most common disease location (n = 61, 78.2%). FC and serum CRP levels were significantly correlated with the number of segments with active inflammation (rho = 0.58, 0.48), number of segments with complications (r = 0.35, 0.31), and US activity score (r = 0.62, 0.54). With FC cutoff values of 100 and 150 μg/g, the concordance rates for patients with active small bowel disease were 78.7% (26/33) and 72.7% (24/33), respectively, which were better than those for other disease locations. Conclusions: Disease activity determined by IUS was significantly correlated with the biomarkers, with a better concordance rate in patients with active small bowel disease than in those with other disease locations with FC cut-off values of 100 and 150 μg/g.