Hernias

A hernia occurs when an organ or mesentery pushes through an opening in the muscle or tissue that normally holds it in place. Hernias occur most commonly in the abdomen when there is a deficit or weakness in the abdominal wall, but they may also occur at the diaphragm or the perineum.

1) Inguinal

2) Umbilical

3) Perineal

4) Diaphragmatic

5) Post-operative.

1.7.1 Inguinal hernia

The vaginal process develops in the embryo as an extension of the parietal peritoneum. Therefore the cavity of the vaginal process is continuous with the peritoneal cavity via the vaginal ring. In the male of all species and the bitch it is possible for abdominal contents (e.g. small intestine or great omentum) to protrude through the vaginal ring and enter the vaginal process. Within the vaginal process the herniated organ or tissue passes through the ingui­nal canal and may enter the scrotum. An inguinal hernia may or may not be reducible; an irreducible hernia may become strangulated if the blood supply becomes interrupted.

Congenital inguinal hernias are common in pigs, but in sheep they are thought to be a result of trauma. In the horse inheritance has not been proven, but they are more common in certain breeds.

1.7.2 Umbilical hernia

Normally, at birth, the umbilical ring closes and the umbilical blood vessels, the vitelline duct and the allantoic stalk begin to degenerate. If contraction of the umbilical ring does not occur completely it is possible for abdominal contents to enter the aperture and appear as a soft swelling beneath the umbilical scar.

1.7.3 Perineal hernia

The perineum is the part of the body wall that occludes the caudal opening of the pelvic cavity; it surrounds the anus and the urogenital opening. The major portion of the perineum, comprising the levator ani and coccygeus muscles, is called the pelvic dia­phragm.

Perineal hernias occur mainly in older male dogs and certain breeds, e.g. the Boxer, Boston Terrier, Pekingese and crossbreds.

1.7.4 Diaphragmatic hernia

The diaphragm separates the abdominal cavity from the thorax. Sudden increases in pressure in the abdomen can result in tears of the diaphragm with the consequence that abdominal organs can be forced into the thoracic cavity. This situation can occur as the result of a road traffic accident. Congenital hernias of the diaphragm are of rare occur­rence in the dog and horse.

1.7.5 Post-operative hernia

A surgical incision in the abdominal wall is normally closed either with sutures or sta­ples. If there is breakdown along the incision, there is a risk of herniation of abdominal organs. This situation may result from a variety of circumstances, e.g. poor healing of the incision due to inadequate vascularisation, pressure from the weight of the abdomi­nal organs, faulty suturing technique and interference with the wound by the patient.