Veterinarians learn more about horse surgeries
…Part two of two
Last week’s segment discussed upper respiratory topics and orthopedic therapies.
Lisa A. Fortier, DVM, PhD, Dipl. ACVS, associate professor of Large Animal Surgery at Cornell University’s College of Veterinary Medicine in Ithaca, NY, discussed several studies on colic. In the first, researchers evaluated how visualizing colonic mesenteric vasculature (the ability to see blood vessels supplying the large colon) on abdominal ultrasound might indicate right dorsal colon displacement, a 180° volvulus (twist), or both. The team performed abdominal ultrasound on 82 horses before confirming their diagnosis via surgery. Researchers concluded the test has a 68 percent sensitivity (these are true positives, meaning that when clinicians see vessels on ultrasound there is a 68 percent chance that horse will have a displacement or volvulus) and 98 percent specificity (these are true negatives, meaning that 98 percent of horses whose vessels are not apparent on ultrasound do not have a displacement). On that basis, she recommended practitioners implement abdominal ultrasound in their colic examinations. She cautioned that before becoming competent in this technique, veterinarians must familiarize themselves with cecal vascular anatomy, which runs ventral to the right paralumbar fossa (flank) and follows the curvature of the last rib.
Next, Fortier discussed a study in which scientists evaluated the success rates of treating horses medically for suspected right or left dorsal colon displacement. The retrospective study included 116 cases of suspected large colon volvulus and showed that clinicians were 64 percent successful in managing presumed right colon displacement medically and 76 percent successful in treating suspected colon displacement with medical approaches. If surgery was needed, Fortier said, roughly 94 percent survived to discharge. With this study researchers showed that most affected horses will respond favorably to medical therapy, she relayed.
Fortier also touched on a study in which researchers assessed the long-term survival rates of horses with large colon volvulus. The team evaluated the two-year survival rates of 116 horses, and they found that 20 percent did not recover from surgical anesthesia and 71 percent survived to discharge. Of the latter, 48 percent survived one year past discharge and only 34 percent survived two years past discharge. Fortier stressed that veterinarians should refer such cases early to expedite treatment and/or surgery because increased preoperative packed cell volume was strongly associated with decreased survival.
Ness SL, Bain FT, Zantingh AJ, et al. Ultrasonic visualization of colonic mesenteric vasculature as an indicator of large colon right dorsal displacement and/or 180 degree volvulus in horses. Can Vet J 2012; 53(4):378-382.
McGovern KF, Bladon BM, Fraser B, et al. Attempted medical management of suspected ascending colon displacement in horses. Vet Surg 2012; 41:399-403.
Suthers JM, Pinchbeck GL, Proudman CJ, et al. Survival of horses following strangulating large colon volvulus.Equine Vet J 2012 Sep 19. doi: 10.1111/j.2042-3306.2012.00620.x. [Epub ahead of print].
In her final segment, Fortier discussed several studies surrounding racehorse health. Researchers on the first paper evaluated the incidence of racehorse injury among different trainers. The team found that 25 percent of the 647 horses under the care of 13 trainers at six different racetracks sustained a carpal, metacarpophalangeal, and/or metatarsophalangeal (knee and/or fetlock) injury during training; further, there were significant differences in injury rates, location, and severity among the trainers.
“Understanding the differences in training protocols between trainers might lead to methods to decrease injury,” she said. “This might include not only exercise, but training surface, shoeing, medication, and rider.”
In the next study Fortier discussed, scientists had evaluated if there was an association between career length and age of first start among a population of racehorses. A research team evaluated the race records of more than 117,000 Australian Thoroughbreds and found that horses’ risk of retirement was actually lower if horses began racing at 2, had more starts at 2, and ran at longer distances. This suggests that there are no apparent detrimental effects of racing as a 2-year old, she said.
The final study Fortier presented involved subclinical (nonapparent) defects in non-lame Thoroughbred racehorses’ suspensory ligaments as identified with ultrasonography. Two reviewers evaluated ultrasound images from 60 racehorses at the end of a full race season, and they found mild defects (Grade 1) in 26 percent of horses and moderate defects (Grade 2) in 7 percent of horses. The reviewers did not find any defects that could be classified as severe (Grade 3), she said. Further, on follow-up examination, Fortier noted that only one Grade 2 horse’s defects had progressed to a clinical problem.
“This suggests that ultrasound findings are not always correlated with disease and a false diagnosis of suspensory ligament desmitis could negatively affect sales,” she concluded. “If suspensory branch lesions are identified on ultrasound examination, further methods of evaluation such as a full lameness examination should be performed to understand the clinical significance of the ultrasound findings.”
Reed SR, Jackson BJ, McIlwraith CW, et al. Descriptive epidemiology of joint injuries in Thoroughbred racehorses in training. Equine Vet J 2012; 44:13-19.
Ramzan PH, Palmer L, Dallas RS, et al. Subclinical ultrasonographic abnormalities of the suspensory ligament branch of the athletic horse: A survey of 60 Thoroughbred racehorses. Equine Vet J May 20. doi: 10.1111/j.2042-3306.2012.00588.x. [Epub ahead of print].
Velie BD, Knight PK, Thomson PC, et al. The association of age at first start with career length in the Australian Thoroughbred racehorse population. Equine Vet J 2012 Aug 28. doi: 10.1111/j.2042-3306.2012.00651.x. [Epub ahead of print]. F