The equine gastrointestinal system is extensive, with the small intestine measuring 70 feet in length alone. Because the small intestine coils throughout the abdomen, diagnosing a specific lesion in the small intestine is extremely challenging for equine veterinarians.

"Ultrasounding the small intestine is helpful when evaluating horses for chronic colic, weight loss, and protein-losing disorders," advised Tracy E. Norman, VMD, Dipl. ACVIM from the Department of Large Animal Clinical Sciences at Texas A&M University, who presented at the 2010 American Association of Equine Practitoners Convention, held Dec. 4-8 in Baltimore, Md.

Norman and colleagues hypothesized that nasogastric administration of water mixed with mineral oil (administered through a stomach tube) could separate the loops of small intestine and reduce gas in the small intestine. They also thought that fasting the horse could increase the value of an ultrasound examination.

Norman et al. assessed the use of ultrasonograpy in 10 horses which were eating their normal ration, fasted for 24 hours, or fasted and administered an oil/water mixture that acted as a contrast agent