For those inguinal hernias where the intestines remain within the vaginal process or extension of the peritoneal cavity (the lining of the abdomen), conservative management and time can often result in a resolution without the need for surgical intervention. The hernia needs to be manually reduced daily to encourage the intestines to move back into the abdomen and hope that the vaginal ring decreases in size relative to the abdominal contents, thus reducing the risk of the hernia returning. In hernias that occur when the vaginal process tears, usually during foaling due to increased abdominal pressures, the intestines move into the subcutaneous tissues, causing a life-threatening situation that requires urgent veterinary attention.
If surgery is not performed there is a huge risk that the intestines will overstretch the fragile scrotal skin and cause it to ulcerate and tear, exposing the intestines to the environment. Once the intestines are exposed, they are easily damaged or infected, ultimately causing death. During surgical repair of these scrotal hernias, the testicle on the side of the hernia is usually removed, and the open ring sutured closed to eliminate the risk of more intestine moving through it.
When the hernias are left to resolve on their own, castration should be performed when the foal is older as the condition is heritable, and these colts should not be used for breeding purposes. It should be noted, however, that castration carries a risk of evisceration or loss of intestines through the castration site, and it is strongly recommended that any foal with a history of congenital inguinal herniation undergoes a closed castration procedure to minimise the risk of the evisceration. A closed castration is one where the scrotal vessels and tunic is ligated and closed to prevent any abdominal contents moving out through the opening.
Adult male horses can have what is termed an “acquired inguinal hernia”, where some form of strenuous physical activity causes the gut contents to move out through the inguinal ring and into the scrotum. There is some thought that the vaginal ring in these horses is congenitally enlarged and therefore the stallion is predisposed to herniation. Clinically, the stallion will show signs of colic and careful observation will identify a swollen and painful scrotum. There are reports of these hernias being fixed conservatively, however, if there is any evidence that the intestines within the scrotum have been seriously compromised, immediate surgery is required to assess the intestines and repair any damage.
There have been infrequent cases of mares or geldings acquiring an inguinal hernia, however, these are rare as the inguinal ring in mares and geldings are smaller and don’t allow the intestines to move through them.
“False” hernias differ from the true hernias mentioned above in that they occur because of a tear or abnormal hole in a surface that allows an organ or part of an organ to move out through the opening but there is no hernial ring and the contents are not contained within a hernial sac. They are less common than the true hernias and can result in many different clinical signs, depending on what has herniated and where the hernia is. Below are listed some of the various false hernias that can be seen in horses.
INCISIONAL HERNIAS: These occur when a surgical wound into a cavity breaks down and the contents of the cavity bulge out under the skin or subcutaneous tissues, causing a visible soft swelling. The more common incisional hernias occur following an abdominal laparotomy, where circumstances have resulted in the internal sutures weakening and the abdominal contents protruding through the gut wall and sitting on the ventral abdomen.
Multiple abdominal surgeries can predispose a horse to an incisional hernia as the wall is weakened when it is opened and sutured more than once, as can occur with some colic patients that require the surgeons to re-operate when complications occur following the initial surgery. Infection can also lead to wound breakdown and an ensuing hernia. Sometimes a surgeon will apply a body bandage or wrap to the abdomen to try and minimise the risk of the wound breaking down and a hernia occurring.
TRAUMATIC INDUCED HERNIAS: These can occur through the gut wall when the internal muscles are weakened or damaged physically, allowing the abdominal contents to spill out into the subcutaneous tissues, forming a hernia. They are visible as soft fluctuant swellings on the abdominal wall and, depending on their size and location, can be treated either conservatively or surgically.
DIAPHRAGMATIC HERNIAS: Diaphragmatic hernias are rare in horses and can be congenital or acquired. The defect in the diaphragm allows the intestines to go through into the pleural cavity and can result in colic symptoms or respiratory symptoms, depending on how large the defect is and what herniates through. Sometimes only a small hole exists and the intestine that passes through is strangulated, causing severe colic with minimal effect on the respiratory system. In other instances, the hole is large, allowing the intestines to become displaced into the pleural cavity, greatly decreasing the room available for the lungs to expand, resulting in the horse having difficulty breathing. They are usually diagnosed with the ultrasound machine as abdominal contents are visualised in the chest cavity, however, in some cases the abdominal contents are not visible, and surgery is required to diagnose the problem. The success of the surgery will depend on the size and location of the defect in the diaphragm as not all areas of the diaphragm are accessible to the surgeon and euthanasia may be required.
HIATUS HERNIA: A very rare hernia that occurs when the stomach, or part of the stomach, protrudes up through the diaphragm and causes clinical symptoms related to eating and recurring choke episodes. These can be managed conservatively but management changes when the horse eats.
PERINEAL HERNIA: Also very rare, with a single case being reported in a donkey, although more common in other breeds of animals. The perineum in the horse is the area around the anus and vulvar lips (mares) and occurs when the pelvic musculature is damaged or weakened, allowing organs in the hind part of the abdomen to herniate. They appear as soft swellings on one side or the other of the perineum and the hernia can contain intestines, bladder, or rectum. In the case of this donkey, surgery was performed, and the donkey made an uneventful recovery. EQ
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