Hernia refers to the abnormal protrusion of an organ or tissue through a normal or abnormal opening in the abdominal muscles or in the diaphragm. The term is commonly used to denote bulging of organs through the muscular part of the abdominal wall.
Hernias are classified according to type and location. According to type they are:Reducible - the hernia contents can be returned to the abdominal cavity by manipulation.
Irreducible - the hernia contents cannot be returned to the abdominal cavity without surgical intervention; adhesions of the herniated tissues to adjacent structures.
Strangulated - the hernial contents are constricted at or by the hernial ring, resulting in vein congestion and eventual development of endotoxin shock and gangrene of the herniated tissue.
In an umbilical hernia there is a protrusion of omentum, the fat associated with the falciform ligament, or part of an organ through an open umbilical ring. The hernial contents are enclosed in a visible sac composed of skin, subcutaneous tissue and peritoneum. In hernias of the umbilical cord, the viscera pass through the abdominal wall, through a dilated umbilical cord, and are not covered with skin or peritoneum. Umbilical hernias are common and there is no sex predilection, they do, however, show a breed and familiar risk. The incidence is low in the domestic cats however; a high incidence has been shown in Cornishrex cats. Breeds of dogs showing high risks are Airedale Terrier, Basenji, Pekingese, Pointer and Weimeraner. These hernias probably are congenital and hereditary. They result from the failure of abdominal muscles to fully develop. There is evidence that the size of the umbilical ring is governed by two or more recessive genes.
Some animals with umbilical hernias have poorly developed abdominal muscles surrounding the hernia. The rectus muscles and aponeuroses of the two oblique muscles are hypoplastic. The midline of the abdomen appears to consist solely of a wide and thin linea alba that may extend from the xiphoid cartilage to the pubis.
Some umbilical hernias may be acquired. For example, the umbilicus may be enlarged or weakened if the cord is severed too close to the abdominal wall or if the bitch chews the cord, If the umbilical cord is handled carelessly during a cesarean section, umbilical hernias may result.
An obvious protrusion in content of the ventral abdominal wall, cranial to the midpoint between the pubis and xiphoid cartilage. The hernial sac size will vary but usually is small. Palpation reveals a soft fluctuating mass that is painless. With gentle manipulation the hernial contents can be returned to the abdominal cavity. When the sac has been ruptured in this manner the umbilical ring can be palpated. Small firm hernias consist of a portion of the falciform ligament or a piece of omentum. These tissues may become adherent to the skin and resist reduction, Large firm masses of the umbilical region may reflect cellulitis, abscess formation, or the presence of intestine. With an abscess or cellulitis, there is inflammation, fever, leukocytosis and pus accumulation, When the intestine becomes strangulated, signs of obstruction are present. This should prompt a radiographic examination.
Most umbilical hernias in puppies are small, firm, irreducible, and of no clinical significance. In the female puppies the hernia may be reduced and corrected when the animal is presented for ovario-hysterectomy. Small hernias in puppies may correct themselves spontaneously before the animal reaches maturity. Periodic reduction of small hernias, together with bandaging, has been attempted to encourage closure of the umbilical ring. This technique has demonstrated limited success. Large hernias require surgical correction to prevent strangulation and for cosmetic reasons.
All operations for umbilical hernias are performed with the patient in dorsal recumbency. With small hernias, a single midline incision is made directly over the hernial sac and extended past the cranial and caudal limits of the ring. For large hernias an elliptical incision and removal of redundant skin may be necessary.
The hernial sac is isolated from its attachment to the skin and subcutis tissue down to and including the umbilical rim. Small hernial sacs that have no internal adhesions may be simply inverted into the abdominal cavity. The edge of the hernial ring is excised and debrided, and then apposed with a series of simple interrupted or horizontal mattress sutures of monofilament steel or PDS.
Closure of a large hernial ring places considerable tension on the sutures, and may require non-absorbable suture material, such as stainless steel, Occasionally adequate apposition will require incising the external lamina of the rectus sheath on each side of the hernial ring.
Removing the fundis of the peritoneal sac and remnants of the urachis is required for large hernias, When the contents of the hernial sac have been replaced in the abdominal cavity, mattress sutures are placed across the neck of the sac and the redundant portion is removed. An alternate method is to expose the hernial sac by making a longitudinal skin incision from a point cranial to the sac to a point caudal to it The skin is removed carefully from the hernial sac and the dissection is continued to expose its neck and the hernial ring. The sac is opened and any adhesions are broken down and the contents are then replaced in the abdominal cavity. The peritoneum is closed at the hernial ring with simple interrupted sutures of PDS and the redundant portion of the sac is removed. The rectus muscles are apposed with a series of interrupted sutures of steel. All fat must be removed from the rectus sheath. The superficial fascia over the rectus muscle is immobilized to form flaps that can be imbricated or pulled medially to overlap the hernial site and reinforce the wound. The skin is closed with non-absorbable sutures or skin staples.