An umbilical hernia in a foal can result from a number of causes. It can be the result of trauma at birth, which may not have been apparent to any onlookers, or a hereditary defect. In the latter, most common cause, the hernia results purely and simply because the muscles around the navel failed to close at birth.
A healthy foal
Hernias are one of the most common problems stemming from birth in foals, and these defects may appear with greater frequency in certain bloodlines.
Whatever the cause, it manifests itself as a bulge where the umbilical cord was or is attached. The swelling is usually part of the peritoneum, a sac of tissue that envelops the internal organs. A hernia may also contain part of the intestine.
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.
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.
Umbilical hernia. This type occurs when the body wall around the umbilical structures fails to form. The incidence of umbilical hernias has been cited in between 0.5 and 2 percent of foals born. They are seen equally in males and females. Their size is usually gauged by the number of fingers that can be inserted into them.
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. 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.
An inguinal hernia in a male foal often resolves spontaneously during the first year of life. For this reason, early corrective surgery is not indicated unless the hernia is strangulated or of such magnitude that it interferes with gait.