Umbilical Hernia

Also known as: Omphalocoele

Do not confuse with: Patent or Persistent Urachus

Introduction

Umbilical hernias occur at the site of umbilicus, the point at which the animal was previously joined to the placenta by the umbilical cord. Congenital hernias occur due to a failure of complete fusion between the embryological lateral folds, leaving a defect in the ventral body wall through which organs may be able to herniate. Most umbilical hernias are small, reducible and cause few clinical signs. In some cases however, the hernia may contain intestine that becomes incarcerated and strangulated causing acute clinical signs. Strangulation is most likely when the size of hernial ring approximates the size of the diameter of the small intestine. These hernias may occur with other congenital defects, including cardiac septal anomalies, bladder exstrophy, hypospadia, cryptorchidism and peritoneopericardial diaphragmatic hernias. The structures most commonly herniated are the omentum, falciform fat and intestine and they are contained with a hernial sac comprising the skin, the subcutaneous connective tissue and the parietal peritoneum. Unusually, a very large congenital defect in the ventral body wall may occur (an omphalocoele) that leads to the eventration of entire organs and death shortly after birth.

Acquired hernias may form if excessive traction is applied to the umbilical stump before it has contracted completely or if the stump is ligated too close to the abdominal wall.

Signalment

Congenital umbilical hernias occur commonly in all of the major domestic species and the condition may be inherited in the Pekingese and Basenji breeds. It is generally recommended not to breed from animals (dam or sire) whose offspring show this defect although, in farm animals, it is often only the ram or bull that is changed before the next breeding season.

Diagnosis

Clinical Signs

A soft swelling will be palpable in the region of the umbilicus. Simple hernias should not be warm or painful to touch and if either sign is present, differential diagnoses such as umbilical abscess or omphalitis should be considered. In most cases, the hernia is reducible, especially if the animal is in dorsal recumbency.

If a loop of small intestine has become incarcerated and strangulated, the animals may be severely ill and show signs of:

• Vomiting with acute onset
• Depression, lethargy and anorexia

If the intestine ruptures, septic peritonitis may develop with pyrexia and septic shock.

Laboratory Tests

Umbilical hernias are externally evident but changes will be detected on haematological and biochemical profiles if intestine is strangulated.

Diagnostic Imaging

Ultrasonography can be used to determine whether any structures lie within the hernial sac and to ascertain whether the umbilical structures are normal. Imaging can also be used to determine whether the animal suffers from any of the other congenital abnormalities.

Treatment

Surgical herniorraphy is the treatment of choice but, in most cases where the hernial ring is smaller or larger than the diameter of the small intestine, this should be delayed for several months as many hernias close naturally over time. Urgent surgical intervention is required in animals showing signs of intestinal obstruction or strangulation.

An incision is generally made through the skin over or beside the hernial sac and the contents are pushed back into the abdomen, twisting the sac to ensure that no structures remain. In a closed herniorraphy, the sac is then ligated at its base and the skin incision is closed. In an open herniorraphy, the hernial sac is also incised and the contents pushed back into the abdomen in the same way. This variant of the technique is useful to break down adhesions that may have formed between herniated organs and the hernial sac.

In large animals, large deficits in the ventral abdominal wall have traditionally been closed with a 'vest over pants' modified Mayo mattress suture pattern. It has been shown however that this pattern increases the risk of wound dehiscence, with the rate of dehiscence in direct proportion to the degree of overlap that this suture achieves between the two sides of the defect. An appositional mattress sutures (such as a cruciate) is therefore now recommended.

Prognosis

The prognosis for surgical herniorraphy is excellent in uncomplicated cases but worse if intestinal loops have become strangulated or rupture.

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