HERNIAS IN HORSES
Abdominal hernias, the unnatural protrusion of intestine or other tissues through an opening in the body, can develop from several causes. Some are secondary to trauma, including postoperative hernias, which occur when abdominal contents press through an incompletely healed incision site in the abdominal wall. Horses can also develop hernias from natural causes. Two types of congenital hernia are most common:
Umbilical hernias may occur when the umbilical ring—the dense, fibrous tissue that surrounds the umbilicus—fails to close properly after the foal is born. Swelling may appear at the foal’s navel within the first few weeks of life. Smaller hernias, of less than three centimeters, may resolve without treatment as the foal grows. Your veterinarian may recommend manually massaging the contents of the hernia back up into the abdomen each day until the ring closes on its own. If the hernia is still present after six months, or if it is large and protuberant to start with, surgical closure may be necessary.
Inguinal hernias occur in one of the inguinal canals—natural openings in the abdominal wall where blood vessels, nerves and other structures pass through to the structures of the groin, including the testes in male horses and the udders in mares. When abdominal tissues extend into the testes, they may also be called scrotal hernias. Inguinal hernias can occur as congenital defects in foals or in mares who experience difficulty giving birth or other trauma, but they are most common as a complication following castration. Surgical correction is usually required.
Another, rarer, form of abdominal hernia is diaphragmatic— when the intestines, stomach or other tissues may protrude into the thoracic cavity through tears or defects in the diaphragm, the muscular partition that separates the heart and lungs from the digestive organs. This can occur where the esophagus passes through to the stomach (called a hiatal hernia) or through a tear resulting from trauma. Surgical repair of a diaphragmatic hernia is possible, especially if the defect is small and the damage to the intestines is minimal. But the prognosis is generally poor: In one study of 44 horses admitted to either the New Bolton Center at the University of Pennsylvania or the Marion duPont Scott Equine Medical Center in Leesburg, Virginia, 18 died or were euthanatized prior to surgery, and only five survived one year post-surgery. In another study of 31 horses admitted to Hagyard Equine Medical Institute in Lexington, Kentucky, and the University of California– Davis Veterinary Medical Teaching Hospital, only 46 percent (six of 13) who underwent surgery survived to discharge, for an overall survival rate of 23 percent for those diagnosed with the condition.