Intestinal ultrasound in inflammatory bowel disease

Inflammatory bowel disease (IBD) requires accurate monitoring of disease activity. While endoscopy remains the reference standard, it is invasive, costly, and cannot be performed frequently. Intestinal ultrasound (IUS) offers a non-invasive, real-time alternative to assess transmural disease activity. Beyond conventional B-mode ultrasound, advanced modalities such as small intestine contrast ultrasound (SICUS), contrast-enhanced ultrasound (CEUS) and shear-wave elastography (SWE) may provide additional information on disease activity and bowel wall characteristics. The first part of this thesis focuses on the role of IUS in Crohn’s disease (CD). We found that transabdominal B-mode IUS reliably detects intra-abdominal complications, with performance further enhanced by SICUS and CEUS. Additionally, transperineal ultrasound is highly accurate for identifying perianal fistulas and abscesses. Together, these findings support the use of IUS as a first-line diagnostic tool for CD-related complications. In patients undergoing ileocecal resection, combining early IUS with faecal calprotectin demonstrated prediction of endoscopic recurrence, offering the opportunity for timely treatment escalation and improved outcomes. The second part of this thesis focuses on the role of IUS in ulcerative colitis (UC). During filgotinib therapy, we observed that early B-mode IUS changes predicted endoscopic response, while SWE showed no predictive value. In UC patients undergoing colectomy, we found that submucosal hyper-echogenicity corresponded to fat deposition, and when quantified as relative submucosal echogenicity in a prospective cohort, it predicted treatment non-response. Pre-operative sonographic assessment of the appendix revealed distinct features in UC patients who responded to appendectomy. Based on these findings, we developed a pathway to guide decision-making between appendectomy and anti-inflammatory therapy. Finally, hyperbaric oxygen therapy (HBOT) was well-tolerated in therapy-refractory UC patients, with CEUS demonstrating a unique vascular response suggestive of regenerative mechanisms beyond conventional anti-inflammatory effects. Together, these findings highlight IUS as a versatile tool for monitoring disease activity, predicting treatment response, and guiding individualized management strategies in IBD.