Intestinal ultrasound in the assessment of complicated Crohn's disease: a comprehensive review.

Crohn's disease (CD) frequently progresses to stricturing or penetrating behavior, which often necessitates surgical or interventional management. Accurate, real-time assessment of these complications is essential for optimizing therapeutic strategies. This review summarizes the current evidence on the utility of intestinal ultrasound (IUS) and its advanced modalities in diagnosing, characterizing, and monitoring complicated CD. As a noninvasive, radiation-free, and cost-effective point-of-care tool, IUS demonstrates high diagnostic accuracy for detecting intestinal strictures, comparable to computed tomography and magnetic resonance enterography, and its diagnostic performance can be further enhanced by the use of small intestine contrast ultrasonography (SICUS). While differentiating between inflammatory and fibrotic strictures remains a critical clinical challenge, advanced techniques such as contrast-enhanced ultrasound (CEUS) and elastography are actively being investigated for elucidating the nature of stricture, albeit with heterogeneous results to date. Recent standardization of sonographic criteria for strictures has been proposed, with further clinical validation highly anticipated. Furthermore, IUS exhibits strong diagnostic performance in detecting penetrating complications, including abscess and fistulas. The diagnostic yield for these lesions is significantly enhanced by SICUS, which utilizes luminal distension to better visualize extra-luminal tracts. Notably, CEUS plays an important role in distinguishing true avascular abscesses from phlegmons. In conclusion, IUS has established itself as a highly reliable imaging modality for the evaluation of complicated CD. The utility of IUS is expected to grow, driving further research and optimizing point-of-care management for complicated CD.