Ultrasound is extremely useful for imaging the horse's abdomen in cases of abdominal pain or suspected abdominal disease.

Ultrasound produces sound waves that pass through the tissues and bounce back to the transducer at different speeds, depending on the density of the tissues it passes through. This pattern is converted into an image by a computer.

The hair is wet well with alcohol to allow the ultrasound beam to penetrate the hair coat. The ultrasound probe is placed in particular locations and through a particular exam sequence to visualize the accessible structures. Horses with heavy coats may need to be clipped. The size, location and tissue appearance all are evaluated.

The left and right kidneys, liver, spleen, stomach, small intestine, large intestine, bladder, body wall, peritoneal space can all be evaluated to some degree. Findings might include increases in wall thickness indicating swelling, abnormal positioning of a particular segment, overfilling (distention) with gas or fluid. In addition, peritoneal fluid amounts and character (cellular, clear, containing debris) can also be determined. Normal peritoneal fluid appears black on ultrasound- clear fluid.