Intestinal Ultrasonography Diagnostic Performance and Feasibility in IBD during Pregnancy: A Systematic Review and Narrative Synthesis.

Introduction: Inflammatory bowel diseases (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), are associated to poor maternal and foetal outcomes during pregnancy, requiring a strict monitoring of the disease activity, preferably with non-invasive modalities. There are numerous data confirming intestinal ultrasonography (IUS) accuracy and efficacy for the detection of IBD disease activity and complications, but data in pregnant IBD patients are scarce. We aimed to evaluate the diagnostic performance and feasibility of IUS to monitor IBD activity throughout pregnancy. Methods: A systematic literature review was performed to identify studies on the use of ultrasound modality in pregnant inflammatory bowel disease women from the date of inception until April 2024 using MEDLINE, Cochrane Library, EMBASE, and ISI Web of Science databases, with keywords including (1) ultrasound/ultrasonography, (2) pregnancy, and (3) IBD (CD and UC). Additional relevant studies were identified from cross-referencing and hand-searches of references of the retrieved articles. We included fully published observational studies and abstracts. Results: Overall, five studies have been selected from 264 citations. All studies were highly heterogeneous in the definition of disease activity as reference standard, IUS protocols, and outcomes. Two of them used a cut-off value of faecal calprotectin (FCP) >100 μg/g. In one of them, clinical scores were used when the FCP value was ≥100-249 μg/g and FCP ≥250 μg/g was considered as an active disease independently of clinical scores. Only one study used a single reference standard with a Harvey-Bradshaw Index (HBI) >4. Across these 3 studies, results suggest a relatively good specificity (range 83-98%) but low sensitivity (range 33-84%) to detect disease's activity. Only 1 study analysed IUS performance in detecting remission with a sensitivity of 80% and a specificity of 92% compared to the reference standard. The size of the uterus limits the visualization of the terminal ileum and the sigmoid from the second trimester and the third trimester, respectively. The evaluation of the rectum remains limited. Conclusion: IUS appears to offer a practical, readily available and non-invasive means of monitoring disease activity in IBD pregnant women. However, existing literature on IUS accuracy is limited and further studies with standardized reference comparator are needed.