DAY 1 - Correlation and Assessment of Small Bowel Lesions Using Cross-Sectional Imaging Techniques vs Small Intestinal Contrast UltraSonography in Known Crohn’s Disease (CACTUS-CD Trial)

Accurate assessment of small bowel involvement in Crohn's disease (CD) can help guide appropriate treatment and monitor disease progression. While magnetic resonance enterography (MRE) and computed tomography enterography (CTE) are considered superior methods for assessing small bowel Crohn's disease, the potential role of small intestinal contrast ultrasound (SICUS) in monitoring Crohn's disease activity has garnered attention from researchers and clinicians.
 
At the American College of Gastroenterology (ACG) 2024 Annual Scientific Meeting in Philadelphia, Pennsylvania, Dr. Partha Pal, an ACG Outstanding Research Awardee and Consultant gastroenterologist at the Asian Institute of Gastroenterology in Hyderabad, Telangana, India, presented data from the CACTUS-CD Trial (Clinicaltrials.gov: NCT06125678). This study aimed to evaluate the effectiveness of SICUS in improving the detection of small bowel complications associated with Crohn's disease, such as strictures and fistulas.
 
The CACTUS-CD Trial was designed to address the limitations of conventional diagnostic tools in detecting and characterizing small bowel Crohn's disease. While intestinal ultrasound (IUS) is widely available, non-invasive, and relatively inexpensive, it has traditionally been considered less accurate than cross-sectional imaging techniques like CT and MRI. Dr. Pal and his team sought to determine whether SICUS could bridge this gap in diagnostic performance, potentially offering a more accessible and cost-effective alternative for monitoring Crohn's disease activity. 

Dr. Pal explained the primary objective, "The primary outcome of the study was to compare the accuracy for the presence and extent of small bowel involvement in established processes." He elaborated on the secondary outcomes, "The secondary outcomes were to correlate the maximum bowel wall thickness and length of involvement measured by ultrasound with CT or MRE findings, assessing the detection of complications like strictures and fistulas, and evaluating the impact on overall management decisions."
 
The study included 111 adult patients with established small bowel CD. Each participant underwent a SICUS examination before receiving either CTE or MRE, allowing for a direct comparison between the imaging modalities. The results of the CACTUS-CD Trial demonstrated the potential of SICUS as a reliable tool for monitoring small bowel Crohn's disease. SICUS showed high accuracy (95.5%) in detecting small bowel disease, with excellent sensitivity (95.2%) and specificity (100%). These figures suggest that SICUS can effectively identify the presence of Crohn's disease in the small bowel, with a very low rate of false positives or negatives.
 
In terms of determining disease extent, SICUS also performed well, showing 87.4% accuracy, 87.4%sensitivity, and 87.5%specificity. This indicates that SICUS can not only detect the presence of disease but also provide valuable information about how much of the small bowel is affected. This information is useful for treatment planning and monitoring disease progression.
 
One of the most promising aspects of the study was SICUS's effectiveness in identifying complications associated with Crohn's disease. The technique demonstrated 88.3% accuracy for detecting strictures and an impressive 98.2% accuracy for identifying fistulas. These findings suggest that SICUS could be particularly useful in detecting and monitoring these serious complications, which often require specific management strategies or surgical intervention.
 
Furthermore, the measurements of bowel wall thickness and length of involvement obtained through SICUS correlated strongly with those from cross-sectional imaging. This correlation adds credibility to SICUS as a reliable alternative to MRE and CTE for assessing these important disease parameters.

Despite these promising results, Dr. Pal revealed some limitations of SICUS. The technique had difficulties detecting lesions in the proximal and mid-small bowel, areas that are traditionally challenging to visualize with ultrasound. Additionally, in 17% of cases (19 patients), the results from CTE/MRE led to changes in management that would not have occurred based on SICUS alone. This finding underscores the continued value of cross-sectional imaging in certain cases, particularly for assessing proximal and mid-small bowel involvement. Dr. Pal noted that the CACTUS-CD Trial faced some methodological limitations that should be considered when interpreting its results. The non-uniform use of cross-sectional imaging techniques as the reference standard could have introduced variability in the comparison between ultrasound and cross-sectional imaging. Additionally, the study used existing mid-end ultrasound machines rather than higher-frequency ones, which may have impacted the resolution and detail of the SICUS images. The relatively small sample size of patients with established Crohn's disease also limits the generalizability of the findings to broader patient populations.
 
Despite these limitations, the implications of this research are significant as the study suggests that SICUS can accurately identify small bowel Crohn's disease activity, extent, and complications, with only a limited impact on management decisions compared to cross-sectional imaging. This finding is particularly important given the advantages of ultrasound in terms of accessibility, cost, and lack of radiation exposure.
 
Dr. Pal's research has the potential to guide clinical decision-making and management in several ways. First, it provides valuable insights into the impact of different imaging modalities on clinical management decisions, particularly for surgical planning. Second, by offering evidence-based guidance on the optimal use of imaging tools, this research can help improve patient outcomes and reduce unnecessary interventions.
 
The CACTUS-CD Trial raises several important questions for future research. There is a need to evaluate the diagnostic performance of higher-frequency ultrasound machines compared to lower-frequency ones and cross-sectional imaging. Additionally, assessing the impact of standardized cross-sectional imaging protocols on the comparison between ultrasound and the reference standard could provide more robust evidence. Further research is also needed to explore the diagnostic capabilities of these modalities in patients with suspected small bowel disease, as opposed to those with established diagnoses. Finally, investigating the influence of operator experience on the performance of ultrasound could help standardize the use of SICUS in clinical practice.
 
The CACTUS-CD Trial represents a significant step forward in optimizing the diagnosis and monitoring of small bowel Crohn's disease. While SICUS may not entirely replace cross-sectional imaging techniques, it offers a promising complementary tool that could improve patient care, reduce healthcare costs, and minimize radiation exposure. As further research addresses the questions raised by this study, SICUS may become an increasingly valuable asset in the management of Crohn's disease, potentially changing the landscape of gastrointestinal imaging in the years to come.