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.
These hernias are characterized by protrusion of intestine or other viscera through the inguinal canal. They are fairly common
in the dog and occur more frequently in bitches. Ingninal hernias are not common in the cat. In the bitch inguinal hernias
are found most often in the pregnant or old intact animal and the hernial sac may contain a gravid or diseased uterus. Inguinal
hernias are rare in the male dog. when present it may extend to become an inguinoscrotal hernia, Inguinal hernias in puppies
may disappear spontaneously, Predisposition to inguinal hernia has been suggested and it may have a hereditary basis. A structural
weakness can be present in the inguinal area of the bitch, The frequencies of inguinal hernia in a pregnant birch may be attributed
to increased abdominal pressure. Obesity can be a predisposing factor The resistance of the mammalian inguinal region to herniation
of viscera may depend on the neuromuscular reflex mechanism of the lower abdominal wall rather than on the resistance of the
inguinal rings. Whether the lesion is congenital or acquired, there seems to be a structural defect in the region. The internal
and external rings are almost superimposed and there is no intervening canal; thus a gap is present in the abdominal floor.
Inguinal hernia is manifested by a protrusion of abdominal contents near the inguinal canal, Although most inguinal hernias
are unilateral, careful examination may reveal the condition to be bilateral, The hernial contents are soft, doughy, and painless
on palpation; this varies, however, depending on the contents and length of time that the hernia has been present. The swelling
may be so small as to be obscured by the candal mammary glands or fat pads. The swelling might be large enough to contain
a gravid uterus or one with pyometra. When the hernia extends beyond the external ring in a caudal direction (labial hernia)
it may be lateral to the vulva and may resemble a perineal hernia.
If the hernia is easily reduced, determining the location of the hernial ring is possible. Reduction of the hernia may be
assisted by elevating the hindquarters while the animal is in dorsal recumbency. When pressure in the caudal portion of the
abdominal cavity is thus reduced, the hernial ring may be palpable.
If it is difficult or impossible to reduce the hernia because of incarceration or strangulation of intestine or growth of
a fetus after herniation of the uterus, the diagnosis becomes more difficult, The swelling may be confnsed with a mammary
tumor, cyst, hematoma or abscess.
An abscess is usually warm and accompanied by fever and leukocytosis. There are usually signs of pain when an abscess is palpated
and the swelling is not so freely movable as that of a hernia, Cysts and hematomas are not warm and usually take considerable
time to develop. These are most easily diagnosed by palpation,' they are firm and may be lobulated or nodular. Lipomas in
the inguinal region may be difficult to differentiate from a hernia, however It must be kept in mind that a mammary gland
or tumor may conceal a small hernia.
Exploratory puncture and aspiration of the swelling contents have been advocated as a diagnostic measure, but this should
be done with caution.
Radiography is helpful to differentiate intestine, gravid uterus, or bladder in the hernial sac, Barium contrast material
is helpful if the digestive tract is involved. When the herniated uterus is gravid and in late gestation, the fetal skeleton
will be visible on scout films, If gestation has been less than 43 days, a lobulated fluid density will be apparent.
When the bladder is involved, signs of cystitis are associated with the hernia. After administration of 10% Sodium Iodide
or air, a cysrogram will reveal the presence of the bladder in the sac. A decrease in the size of the hernia may be observed
following urination or urinary bladder catheterization. Although some inguinal hernias may be readily diagnosed, in others
the bulge in the inguinal region may be so insignificant as to defy detection, Only a small portion of the intestine may be
incarcerated in the inner ring. These animals are presented with signs of intestinal obstruction. The cause of such a radiographically
demonstrable obstruction may be ascertained only by exploratory laparotomy.
Ventral midline approach is used for all inguinal hernias allowing utilization of both inguinal rings and repair of bilateral
hernias through a single incision. In addition, this incision maybe extended cranially without disruption of the mammary tissue
or its' blood supply.
The incision is made from the cranial brirn of the pelvis and brought cranial until adequate exposune of the sac is accomplished.
Undermining of the mammary tissue and lateral retraction allows for exposure of the ingninal ring and sac. Blunt dissection
frees the sac from the subcutaneous tissue. The hernial sac is opened and inspected Adhesions between tbe sac and viscera
are removed and sac contents are returned to the abdominal cavity.
Often enlargement of the inguinal ring is accomplished in order to ease hernial reduction. Should bladder be included, aspiration
simplifies the procedure.
After organ replacement, the sac is trimmed at the margins of the inguinal ring and the hernial ring sutured with simple interrupted
(2-0) stainless steel.
Inspection is made of the opposite inguinal ring, vaginal process removed and inguinal ring sutured closed. Mammary tissue
is replaced and a penrose drain inserted. Routine dosure of skin follows.
Post-operative care includes an abdominal wrap bandage which eliminates dead space and helps the comfort of the patient. Drains
are removed 3 - 5 days post-operatively.