Colic Emergency!

A 10-year-old Thoroughbred broodmare awaits her morning meal. There is a 4-month-old foal by her side. She only eats about half of the ration, but shows no signs of distress. The barn manager is notified that his best mare is a bit off her feed and showing mild signs of depression. In the short time it takes him to get to the barn, the mare has begun circling her stall and pawing occasionally. In 30 minutes when the veterinarian arrives, the mare is sweating and her abdomen is distended. She is trying to lie down. With some coaxing she remains standing for a brief physical exam. Her heart and respiration rates are elevated and her oral mucous membranes are pale. No sounds of intestinal movement can be heard. Rectal examination reveals a very gas-distended large intestine. The tentative diagnosis is large colon torsion, also known as large colon volvulus.

The veterinarian quickly administers an analgesic for pain and passes a nasogastric tube to relieve fluid or gas distention of the stomach. She explains that the colon has likely twisted, obstructing the lumen (space within the colon) and cutting off the blood supply. For reasons not fully understood, broodmares four to 12 years old and three to six months post-foaling are particularly predisposed to this problem. The only hope to save the horse is a quick trip to a referral hospital and possibly emergency colic surgery.

The referral hospital is alerted and the colic team gets ready. The mare is loaded for the 45-minute trip. The foal is left at home.

Upon presentation at the referral hospital, the mare's abdomen is even more distended. Her mucous membranes have become bright red with increased capillary refill time. She is panting, sweating, and is in a lot of pain. She is taken across the weight scale and directly to the padded anesthesia drop area in case she lies down during the surgeon's examination. Analgesics are judiciously administered to keep the mare comfortable long enough to draw blood for pre-operative analysis, place an intravenous catheter, administer antibiotics and Banamine, and lavage her mouth to remove any feed material.

The mare is anesthetized and prepared for surgery. The prep must be thorough but quick, since the distended colon is placing pressure on the diaphragm, reducing the lungs' ability to expand, even with a respirator. The colon distention is also blocking venous blood return to the heart, impairing normal circulation.

With the mare on her back, surgeons use a midline incision. The gas-distended large colon is decompressed with a needle attached to a vacuum bottle. Exploration of abdominal contents reveals a 360-degree rotation of the colon where it attaches to the cecum.

Once partially decompressed, the colon torsion is partially corrected while still in the abdominal cavity. Then the colon is carefully lifted from the abdomen and rotated. A team effort corrects the torsion and places the colon on a tray to empty the contents through an incision (enterotomy). The surgeon performing the enterotomy pays particular attention to the color of the colon lining (mucosa) during the incision. The mucosal color can range from the normal red with profuse bleeding to black with no bleeding (in cases which have gone on for an extended time). This information is important in predicting whether the colon can survive.

Fortunately, the surgeon reports a moderately darkened mucosa with adequate bleeding. This is good news for this mare because the torsion occurred at a level that could not be exteriorized for complete removal (colon resection). A delay in getting this mare to surgery would most likely have resulted in a non-viable colon and euthanasia.

The surgery is completed, and the mare goes to recovery. The chief surgeon informs the farm manager and referring veterinarian that although the outlook will be guarded for several days, this horse has a better chance than most for full recovery due to their close observation and rapid response.

Large colon torsion is one of the most severe and life-threatening forms of colic. Although survival of horses with large colon torsion can be as high as 80-90%, the overall survival rate is 30-50% due to delays in transport or performing surgery. If portions of the colon die in the days following surgery, a second surgery is required to remove the compromised bowel. Complications during the postoperative period are also influenced by the severity of the tissue damage prior to surgery. The longer and more severe the reduction in blood flow to the colon, the worse the injury and the sicker the horse will be after surgery, resulting in a poorer prognosis and requiring a longer period of intensive care with greater costs.

In spite of much progress in farm management, parasite control, and advanced medical and surgical treatments, colic remains second only to old age as the number one cause of death in horses. This case was chosen as a real-life example of how a proactive approach to colic and other emergencies by the farm staff, referring veterinarian, and referral hospital can make the difference in saving a valuable horse.

About the Author

Byron L. Young, DVM, MS

Byron L. Young, DVM, MS, is a clinical instructor in equine surgery and emergency care at the Marion DuPont Scott Equine Medical Center in Leesburg, Va.

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