Introduction

Intestinal ultrasound (IUS) is a non-invasive modality for monitoring disease activity in inflammatory bowel disease (IBD). While widely used for long-term assessment, its utility in early response evaluation following biologic therapy initiation or modification remains underexplored.

Aims & Methods

This prospective study aimed to assess early ultrasonographic response at week 6 in ulcerative colitis (UC) and Crohn’s disease (CD) patients undergoing induction, dose escalation, or switching of biologic therapy. A total of 24 patients (mean age: 40.1 ± 12.8 years; 54.2% female) were included. Fourteen patients (58.3%) were initiating biologic treatment, 4 (16.7%) underwent dose escalation, and 6 (25%) were switched to another biologic agent. Biologic therapies included infliximab (70.8%), adalimumab (16.7%), and others (12.5%). IUS examination was performed at baseline and at week 6. The following parameters were assessed: bowel wall thickness (BWT), wall stratification, color doppler signal activity and mesenteric fat inflammation. IUS remission was defined as bowel wall thickness less than 3 mm and no color doppler signal. IUS improvement was defined as more than 25% decrease in bowel wall thickness without increase in color doppler signal. IUS activity assesment was performed at the same segment of the bowel at the 6th weeks.

Results

A total of 24 patients were included in the study, with a mean age of 40.1 ± 12.8 years; 13 (54.2%) were female. Seven patients (29.2%) had ulcerative colitis (UC), and 17 (70.8%) had Crohn’s disease (CD). Fourteen patients (58.3%) had newly initiated biologic therapy, 4 (16.7%) underwent dose escalation, and 6 (25%) were switched to a different biologic agent. Anti-TNF agents were used in 21 patients (87.5%), including infliximab in 17 (70.8%) and adalimumab in 4 (16.7%). The remaining 3 patients (12.5%) were treated with other biologic agents. At baseline, the most active intestinal segment on IUS was the terminal ileum in CD patients (9 patients, 52.9%) and the sigmoid colon in UC patients (4 patients, 57.1%) (p = 0.021). At week 6, 11 patients (45.8%) showed ultrasonographic improvement, 9 patients (37.5%) had no change, and 4 patients (16.7%) showed worsening. The baseline mean bowel wall thickness (BWT) of the most active segment was 5.5 ± 1.3 mm, which decreased to 4.4 ± 1.7 mm at week 6. A reduction in BWT was observed in 18 patients (75%), while an increase was seen in 6 patients (25%) (p = 0.002). In multivariate regression analysis, higher baseline bowel wall thickness was identified as an independent predictor of ultrasonographic improvement at week 6 (OR: 3.137; 95% CI: 1.005–9.790; p = 0.04). In patients who showed improvement, bowel wall thickness significantly decreased from baseline 6.2 ± 1.5 mm to 3.7 ± 1.6 mm at week 6 (to; p = 0.003), whereas in patients who worsened, an increase in wall thickness was observed (5.3 ± 1.0 mm to 6.7 ± 1.7 mm; p = 0.068). By disease group, 5 of the UC patients (71.4%) showed ultrasonographic improvement, 1 (14.3%) remained unchanged, and 1 (14.3%) worsened. Among CD patients, 6 (35.3%) showed improvement, 8 (47.1%) had no change, and 3 (17.6%) worsened. However, there was no statistically significant difference in response patterns between the UC and CD groups (p = 0.244).

Conclusion

Intestinal ultrasound at week 6 effectively detected early treatment response, with baseline bowel wall thickness emerging as a predictor of improvement. These results support its use in routine early monitoring of IBD patients on biologic therapy.

References

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