Intestinal ultrasound for monitoring postoperative Crohn’s disease: A systematic review and clinical implications

Abstract

BACKGROUND

Postoperative recurrence is common in Crohn’s disease (CD), with endoscopic lesions in a majority of patients by 12 months after surgery. Ileocolonoscopy is the reference standard but is invasive and poorly suited to frequent surveillance. Intestinal ultrasound (IUS) - including small intestine contrast ultrasound and contrast enhanced ultrasound - is a repeatable, noninvasive alternative.

AIM

To summarize the evidence on the diagnostic accuracy and prognostic value of IUS for detecting postoperative recurrence in CD.

METHODS

We systematically searched PubMed and EMBASE through June 2025 for original English-language studies evaluating IUS against clinical or endoscopic outcomes in postoperative CD. This scoping review was conducted and reported in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses guideline. After screening 259 unique records, 41 full texts were assessed and 20 studies were included.

RESULTS

Bowel wall thickness thresholds of ≥ 5 mm at the neo-terminal ileum predict endoscopic recurrence with sensitivities 81%-94% and specificities 86%-100%; lower cutoffs at the anastomosis (≥ 3-3.5 mm) also carry risk (data from singlecenter cohorts). Dualsite assessment (neo-terminal ileum + ileocolonic anastomosis) improves performance. Adding Doppler hyperemia or mesenteric lymphadenopathy increases accuracy; combining bowel wall thickness ≥ 3 mm with fecal calprotectin ≥ 50 μg/g yields high specificity (approximately 93%-100%) with a negative predictive value of nearly 95% when both are negative. Contrast enhanced ultrasound-based composite scores reach approximately 98% diagnostic accuracy in prospective cohorts. Small intestine contrast ultrasound shows similarly strong early diagnostic performance - for example, an area under the receiver operating characteristic curve up to 0.95 when using ileocolonic anastomosis wall thickness ≥ 3 mm to 3.5 mm plus lesion length, with 82%-94% sensitivity and > 90% specificity reported even within 7 days post-resection. Overall, IUS shows moderate agreement with endoscopy (κ approximately 0.5-0.8) and stronger prognostic value when performed within 12 months post-surgery.

CONCLUSION

IUS can be integrated into postoperative surveillance algorithms - particularly within the first year - and can reduce routine endoscopy in selected patients. Research priorities include standardized thresholds and composite scoring, consensus training/competency, and multicenter validation including artificial intelligenceassisted interpretation.

Keywords: Postoperative recurrence; Crohn’s disease; Bowel wall thickness; Small intestinal contrast ultrasound; Intestinal ultrasound

Core Tip: Intestinal ultrasound is a practical, non-invasive tool for monitoring postoperative Crohn’s disease. Bowel wall thickness > 3-5 mm, especially when persistent or worsening, predicts recurrence. Diagnostic accuracy improves with dual-site assessment (neo-terminal ileum and ileo-colonic anastomosis), Doppler hyperemia, and lymphadenopathy. Integration with fecal calprotectin enhances specificity and negative predictive value. Advanced techniques like contrast enhanced ultrasound and small intestine contrast ultrasound further refine detection. Early assessment within 12 months post-surgery is most prognostic. Intestinal ultrasound is well-suited for repeated follow-up, and when used systematically, may reduce reliance on routine ileocolonoscopy in selected postoperative patients.