Use of ultrasonography to diagnose large colon volvulus in horses

OBJECTIVE: To describe the use of ultrasonography to diagnose large colon volvulus (LCV) in horses. DESIGN: Descriptive report. ANIMALS: 4 horses with clinical signs of abdominal pain. PROCEDURE: Each horse was administered analgesic agents for pain control and placed in stocks. Ultrasonographic evaluations were performed with a 3.5-MHz sector scanning transducer that was placed parallel to the long axis of the horse (longitudinal imaging) over an area of the left ventral aspect of the abdomen. The boundaries of the evaluated region included the ventral midline, 2 vertical lines at the level of the left 10th and 17th intercostal spaces, and a horizontal line between the 2 vertical lines at the level of the costal arch of the left 10th intercostal area. RESULTS: In all horses, nonsacculated large colon was identified ultrasonographically in the left ventral portion of the abdomen; this finding was considered indicative of LCV. In 3 horses, the LCV involved intestinal rotation of 180 degrees, whereas in 1 horse, the LCV involved intestinal rotation of 540 degrees. As confirmed by surgical or postmortem findings, the degree and location of the volvulus were correctly estimated from ultrasonographic images. CONCLUSIONS AND CLINICAL RELEVANCE: In horses, this method of diagnosis of LCV appears to be of value regardless of the location at which the rotation of the large colon occurs. Ultrasonographic findings may aid in the earlier diagnosis of LCV in horses, especially at an early stage of the disease when other clinical signs are equivocal.