Canadian researchers exploring the use of a wireless endoscopy capsule to inspect the inside of the equine gastrointestinal tract say the method appears safe, practical and non-invasive.
The “Alicam system” capsule is 11mm in diameter and 33mm long. It contains 4 micro-cameras, mounted at 90° to provide a 360°panoramic view. The cameras are activated by movement (this helps prolong the battery life and so increase the length of the digestive tract that can be imaged.) When activated, the cameras record images at the rate of 20 /second and store them on the capsule’s internal memory chip.
“It can be frustrating for clinicians to diagnose intestinal lesions in horses because no methods allow a thorough examination of the intestinal tract from an internal perspective aboral to the stomach,” the researchers said.
Five healthy adult horses with no signs or history of gastro-intestinal disease from the University of Calgary’s teaching herd were included in the study. Three different protocols in terms of exercise, feeding and water intake were used, and the researchers found that the one giving the most useful images was to starve the horse for 24 hours before introducing the capsule.
Satisfactory images were obtained of the pylorus, major duodenal papilla, individual villi, and ileocecal junction. Visualization of large intestinal mucosa was poor.
Images are available for inspection only once the capsule has passed through the digestive tract and has been retrieved from the manure (using radiography). On average, it took 6.5 days from introduction for the capsule to be retrieved in the manure. Three of the 15 capsules administered during the study by researchers at the University of Calgary were not recovered.
Among the abnormalities identified on the images were mucosal erosion, ulceration and haemorrhage, areas of thickened mucosa, and evidence of parasitism.
The researchers concluded: “this novel endoscopic capsule appears safe, practical, and non-invasive in horses; however, variability in capsule excretion time must be taken into account for clinical application.”
Imaging techniques currently used are mainly limited to gastric and pyloric examination using long endoscopes, or to ultrasonography of the abdomen, which allows visualization of only a portion of the intestinal tract and rarely allows visualization of intraluminal structures. They noted that capsule devices had been approved for human use for over a decade, and had been used successfully in dogs to evaluate both small and large intestinal mucosa.
The researchers noted that several capsule systems have been used in horses and ponies, using radiofrequency technology coupled with external sensors to receive data from the capsule. “However, this can be problematic in adult horses with larger body mass because of decrease in signal strength, which can result in intermittent loss of communication between the capsule signal and the external sensors.” They said the diagnostic capability of these capsule systems was further impeded by short battery life and limited viewing angles.
The research team comprised Mei Steinmann, Stephanie Bond, and Renaud Léguillette, all with the University of Calgary, Rebecca J. Bezugley from Alberta’s Moore Equine Veterinary Centre, and Jill S. Pomrantz from Infiniti Medical in California.
A wireless endoscopy capsule suitable for imaging of the equine stomach and small intestine. Mei Steinmann, Rebecca J. Bezugley, Stephanie L. Bond, Jill S. Pomrantz, and Renaud Léguillette. Journal of Veterinary Internal Medicine. (2020) 34(4): 1622–1630. doi: 10.1111/jvim.15825