Ultrasound to monitor small bowel CD

October 27, 2025

Issue 21

Clinical Question

How does contrast ultrasound compare to CT/MR enterography for monitoring small bowel Crohn’s disease activity?

Editor’s Bottom Line

Small intestinal contrast ultrasound performs well for characterizing small bowel Crohn’s disease but is less reliable for more proximal disease.

Reference

Pal P, Mateen MA, Pooja K, et al. Correlation and assessment of small bowel lesions using cross sectional imaging techniques compared to small intestinal contrast ultrasonography in known Crohn’s disease (the CACTUS-CD study): a paired, prospective, confirmatory study. Am J Gastroenterol. Epub ahead of print Sept 29, 2025. https://journals.lww.com/ajg.aspx

Synopsis

To evaluate whether small intestinal contrast ultrasound (SICUS) could serve as a reliable first-line modality for assessing established Crohn’s disease, the CACTUS-CD study prospectively enrolled 407 patients (median age: 36 years; 60% male) with small bowel Crohn’s disease requiring imaging evaluation at a tertiary center in India.

All patients underwent intestinal ultrasound followed by SICUS after ingestion of 500 mL polyethylene glycol. This was followed by either computed tomography enterography (CTE) (n=215) or magnetic resonance enterography (MRE) (n=192) within 24–48 hours. The cohort included patients with inflammatory-type disease (50%), stricturing disease (44%) and fistulizing disease (3%), with 36% having isolated small bowel involvement. Indications for imaging included disease flare, treatment response monitoring and surveillance of quiescent disease.

Compared to MRE or CTE, SICUS was 95.3% sensitive (95% Confidence Interval [CI]: 92.6–97.1) and 93% specific (95% CI: 81.4–97.6) in detecting active small bowel disease, with a positive predictive value of 99.1% and a negative predictive value of 70.2%. For determining disease extent, the sensitivity of SICUS was 90.7% (95% CI: 87.3–93.3) and the specificity was 90.5% (95% CI: 77.9–96.2). SICUS performed slightly better than conventional intestinal ultrasound (US) for both detecting disease activity (95.3% vs. 94.2% sensitivity) and extent (90.7% vs. 89.6% sensitivity).

SICUS significantly outperformed conventional intestinal US for identifying strictures, with sensitivity improving from 71.3% to 86.8% (p=0.0005) and accuracy rising from 88% to 94.6% with conventional US vs. SICUS, respectively (p=0.0008). The negative predictive value for identifying strictures increased from 83.3% to 91.6% (p=0.009), while SICUS was 91.7% and 87.5% sensitive in detecting fistulas and abscesses, respectively, with specificity exceeding 99% for both complications.

SICUS correlated strongly with cross-sectional imaging approaches for quantitative measures. Spearman correlation coefficients were 0.667 for maximum bowel wall thickness and 0.839 for disease length (both p<0.001). Analysis confirmed excellent agreement, with mean differences of 0.70 mm for wall thickness and 2.9 cm for disease length.

Of 17 active disease cases missed with SICUS, the majority were located in the proximal ileum, the mid ileum or the jejunum. Similarly, there were 22 missed strictures with SICUS, predominantly located in the distal jejunum/proximal ileum and jejunum.

Adding information from cross-sectional imaging modalities altered patient management in 9.3% of cases (38/407). These changes included surgical planning for resection extent (n=7), therapy escalation for newly identified disease (n=10), medical intensification for strictures (n=6), endoscopic intervention (n=2), identification of malignant strictures (n=2) and ruling out false-positive US findings (n=2). CTE changed management in 8.8% of cases while MRE changed management in 9.9%.

 

Details

Study Design: Prospective, paired diagnostic accuracy study
Funding: None
Allocation: Non-randomized; patients received IUS/SICUS followed by either CTE or MRE based on institutional workflow and patient factors
Setting: Single tertiary referral center
Level of Evidence: 2b