Hernias in Foals
Dr. Mary Rose Paradis
A hernia is an abnormal protrusion of part of an organ or tissue through the body wall. Hernias are one of the most common problems stemming from birth in foals, and these defects may appear with greater frequency in certain bloodlines. When there is a defect in the body wall, abdominal contents, such as intestine or fat, can slip through the hole. Hernias are usually evident just after birth, but may not be apparent until the foal is standing or more active. Umbilical hernia. This type occurs when the body wall around the umbilical structures fails to form. The incidence of umbilical hernias has been cited between 0.5 and 2 percent of foals born. They are seen equally in males and females. One can gauge their size by the number of fingers that can be inserted into them.
Hernias are classified by their location, reducibility, and by the nature of their contents. Most congenital hernias in the foal are umbilical, inguinal, or scrotal in location.
Inguinal hernia. The inguinal region of a horse is where the hindleg meets the abdominal wall. In this region, the external opening of the inguinal canal can be felt as a small slit under the skin. There is a comparable opening deep within the body wall, which you cannot feel. Between these holes (in the body wall and externally) is the inguinal canal, where the spermatic cord runs. Obviously, this is a much bigger structure in males. In some males this opening is abnormally large and allows not only normal structures, but intestine to slip into the scrotum. When the aberrant intestine slips as far as the inguinal canal, it is called an "inguinal hernia."
Scrotal Hernia. If the intestine works itself as far as the scrotum, it is called scrotal hernia.
If you can push the contents of the hernia back in, it is called reducible. Most hernias are reducible to a degree. Umbilical hernias are generally easier to reduce than the scrotal hernias because they will often contain less herniated intestine. Laying the foal on his back will facilitate the reduction of an umbilical or scrotal hernia.
If a hernia is non-reducible, there is a concern that the bowel will become entrapped and lose its blood supply. This is an emergency situation. The foals will exhibit colic pain and the swelling may increase. This is called a strangulated hernia.
Hernias are diagnosed on physical examination of the foal through palpation of the umbilical, inguinal, and scrotal areas, or by observation of swelling in these regions. Most hernias are manually reducible, and other causes are not. Colic may be a sign that the bowel is becoming trapped in the hernia sack. The swelling may increase and become painful to palpation.
Umbilical hernias must be differentiated from umbilical swellings from other causes. Umbilical swellings can arise from abscesses or hematomas, for instance. Occasionally swelling in the umbilical region can occur in response to irritating navel dips, such as tincture of iodine. If there is uncertainty about the contents of the hernia sack or if you are concerned that there is an umbilical infection, then an ultrasound examination is necessary. It will differentiate between intestinal structures and other structures that may be within an umbilical swelling.
Many simple hernias resolve within 6 months of age. As the foal continues to grow the body wall defect becomes proportionally smaller. Manual reduction of the hernia several times a day may be helpful. There are other methods used to hasten the closure of umbilical hernias. These may involve the local injection of an irritating substance such as iodine and applying an abdominal wrap to keep the hernia reduced. These methods can be dangerous and must be performed by an experienced veterinarian. Hernia clamps have been used to create inflammation in the underlying tissue and reduce the size of the hernia sack. A figure 8-type bandage or truss can be applied to foals with scrotal hernias after the hernia has been reduced. Care must be taken so that the penis is not incorporated in the bandage.
If the hernia is large and has not responded to the above treatments, then surgical correction of the defect is recommended. Often surgery will be recommended for correction of an inguinal/scrotal hernia. Special care should be taken when colts that have had inguinal hernias as foals are castrated. If the inguinal canal remains abnormally large there is a chance of herniation of the bowel following castration. This is a life-threatening event.
Foals with hernias should be checked daily with palpation and hernia reduction. Owners should be aware of any increase in size, heat or pain. If the foal develops colic then it is important to have your veterinarian evaluate the hernia for possible strangulation.