Contrast-enhanced ultrasound imaging for assessment of intestinal inflammation in rainbow trout

The intestine is essential for nutritional uptake and as a barrier to pathogens. Inflammation of the intestine can result from chemical contaminants, dietary irritants, or disease and may lead to serious health consequences, including reduced growth rates or increased pathogen susceptibility. Traditionally, intestinal inflammation in fish has been detected through histology completed post-mortem through excision and processing of the affected tissue. However, in human clinical settings, tools have been developed to assess intestinal inflammation non-invasively. Contrast-enhanced ultrasound (CEUS) imaging is an important tool for measuring inflammation in patients because it is cost-effective and minimally invasive. Specifically, CEUS allows real-time visualization and quantification of vascular perfusion. Changes in blood flow are typical in areas of inflamed or diseased tissue, and by measuring these changes, it is possible to assess the degree of inflammation. We demonstrate that standard CEUS protocols used for small mammals can be used to quantify vascular perfusion in the intestines of rainbow trout. Our resolution was sufficient to measure a significant difference in perfusion between control and TNBS-inflamed trout intestines, with inflamed intestines showing decreased perfusion. The presence of inflammation in the TNBS-treated intestines was verified ex vivo histologically and was characterized by the thickening of intestinal folds. The minimally invasive nature of CEUS imaging presents the opportunity to evaluate intestinal health in novel ways by allowing for longitudinal observations and avoiding mortality in valuable or at-risk specimens. Recent developments of highly portable, cost-effective CEUS systems will allow broad application of this tool, from industry to research.