Umbilical Hernias

Q:I am currently looking at a filly to purchase. She had an umbilical hernia, which the owner had repaired. I was wondering if this is a heritable condition. What is the likelihood that if this filly was used for breeding purposes in the future, she would pass on umbilical hernias to her offspring? Could a former hernia affect her future athletic performance? Any information you could give me would be greatly appreciated.


A: The umbilical area provides space for the umbilical cord, in which blood vessels and the urachus (duct for urine to flow from the bladder) function to exchange oxygen, nutrients, and urinary wastes between the fetus and the placenta during pregnancy. At delivery, when the cord ruptures, these vessels contract at once to close the circulatory loop within the newborn foal and change the direction of urine flow. In most cases following normal delivery, the cord ruptures easily. If the cord is stretched abruptly or is too thick to separate easily, there can be stretching of the tissues that make up the muscular opening of the abdominal wall, resulting in a larger than normal hole in the wall. This is the origin of an umbilical hernia, which occurs in less than 2% of horses. The extra space allows the tissues that line the abdominal cavity to drop into the ring of the umbilicus, forming the typical "sac" of the hernia.

It is the consensus of those involved with foaling that the behavior of the mare immediately after delivery is important in the formation of hernias. That behavior often is the result of human involvement in the process. When a mare is undisturbed and delivers in a quiet environment, she tends to deliver the foal while lying down, and stays down until the foal be-comes active. By then, the cord either has broken from the foal's movements or will break easily as the mare stands. When human intervention begins before or during delivery and the mare becomes agitated, the chances for the process to remain natural are reduced. (In fact, human activity often will result in delaying the onset of foaling.) When a mare is compelled to jump up prematurely after foaling, the umbilical ring easily can be damaged. Therefore, management of foaling mares can contribute to the manner of separation of the umbilical cord and related damage to the abdominal wall. The incidence of umbilical hernia is lower on farms with calm and competent help than where panic attends every foaling.

It is my opinion, therefore, that genetics plays a small if not inconsequential role in the causes of the umbilical hernias in foals.

Most of these hernias are small, barely allowing two fingers to be inserted in the ring from the outside. Most close spontaneously in a month or two as the ring of tissue shrinks. One complication can be the trapping of a piece of the intestine in the sac as it continues to close, thus strangulating the intestine. That possibility is the main incentive for correcting umbilical hernias.

Your veterinarian might suggest initially that you manually reduce the hernia frequently, pushing the contents of the hernia back into the abdomen every day or so. This type of management also will give you an early alert to changes in the hernia that could signal complications, such as variations in the size or consistency of the defect. If the hernia is still obvious when the foal is four to six months of age, your veterinarian probably will recommend that it be repaired.

Umbilical hernia repair can be accomplished either by applying a "hernia clamp" or by surgical repair. Both approaches require general anesthesia and surgical preparation. The clamp is suitable for smaller hernias, no larger than two inches in diameter. It works by compressing the sides of the hernia with enough pressure to cause the hernia to slough off, while promoting healing underneath the clamp. The foal must be kept under observation during the process, which might take several weeks. Surgical repair is required for larger hernias, but requires a shorter convalescence. The surgical process is more complicated, and thus more expensive.

Ignoring umbilical hernias is not a wise option. The opening can enlarge in response to any additional trauma to the abdomen. Also, the chances of obstruction and incarceration of the intestine are a possibility and could prove to be disastrous.

About the Author

A.C. Asbury, DVM

A. C. (Woody) Asbury received his DVM from Michigan State University in 1956, then spent 21 years in California in breeding farm practice and at UC Davis. He joined the faculty at the University of Florida in 1977 and was involved in teaching, research, and administration until 1996. An Emeritus Professor at Florida, he lives in Kentucky, where he and his wife are developing a small farm.

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