Inguinal Hernia

What is an inguinal hernia?

An inguinal hernia occurs when abdominal organs or tissues push through the inguinal ring (a natural opening in the abdominal wall near the pelvis) and bulge into the groin area. Inguinal hernias may be congenital (present at birth) or acquired (developing later in life, possibly due to muscle weakness or trauma). Inguinal hernias are uncommon in cats.

Are certain dogs more likely to have an inguinal hernia?

Acquired inguinal hernias are more common in middle-aged and older intact, female, toy-breed dogs. Female animals appear predisposed for the following reasons:

• They have a shorter, wider inguinal canal.
• The effect of sex hormones (estrogen) can weaken collagen in the connective tissues in this area.
• The weight of a pregnant uterus or excess fat due to obesity may stretch a weakened inguinal ring.

Excess glucocorticoids in the system (either caused by disease or given as part of disease treatment) can also weaken the abdominal wall.

Congenital hernias are more common in young male, small-breed dogs. Predisposed breeds include the Basenji, Pekingese, poodle, Cairn terrier, and West Highland white terrier. A multiple-gene (polygenic) inheritance mechanism is suspected in Cocker Spaniels and Dachshunds.

Rarely, inguinal hernias may occur secondary to trauma in dogs of any age or sex. Trauma can disrupt and weaken the muscles of the lower abdominal wall and is often accompanied by other hernias in the area.

What are the signs of an inguinal hernia?

An inguinal hernia may appear as swelling on either or both sides of the inguinal (groin) area. If the hernia involves only fat or omentum (a mesh-like latticework that helps nourish and support the intestines), there generally are no systemic signs of illness.

In uncomplicated inguinal hernias, the swollen area is usually soft, not painful, and can be pushed back into place. In complicated inguinal hernias, there is often a much greater degree of swelling. The mass itself is often firm, painful, and cannot be pushed back into the abdomen. The overlying skin is also often bruised or reddened.

In severe cases, such as when abdominal organs become entrapped or strangulated, clinical signs may include:

• Abdominal pain
• Vomiting
• Diarrhea
• Difficulty urinating
• Vaginal discharge or abnormal bleeding
• Bruising of the area
• Lethargy
• Depression

How are inguinal hernias diagnosed?

Your veterinarian may suspect your dog has an inguinal hernia based on a physical examination. They may recommend several tests to confirm the diagnosis and look for other conditions that could affect treatment. These may include:

• Physical examination. Your veterinarian may be able to feel an enlarged inguinal ring in your dog’s groin area.
• Blood and urine tests. Baseline tests, including a complete blood count (to look for an elevated white blood cell count associated with intestinal strangulation) and a serum biochemistry profile (to look for electrolyte imbalances).
• Fine needle aspiration (FNA). Your veterinarian may use a small needle to collect a sample from the swelling (generally best done with guided ultrasound).
• Radiographs (X-rays) or ultrasound. These imaging tests help determine whether abdominal organs are present in the hernia.
• Advanced imaging. Computed tomography (CT) or magnetic resonance imaging (MRI) may be used.

How are inguinal hernias treated?

It is usually best to surgically repair an inguinal hernia at the time of diagnosis, as delaying can result in a more complicated and difficult procedure. Surgery is required immediately if there is evidence of the bladder, intestinal contents, or uterus trapped in the hernia. Peritonitis (inflammation of the abdominal cavity) or severe pain also indicates the need for immediate surgery.

The goal of surgery is to return the hernia contents back into the abdomen, remove any damaged tissue if necessary, and close the hernia. The surgical approach depends on the preference of the veterinary surgeon and which organs or tissues may be involved.

What is the prognosis?

Congenital inguinal hernias may resolve on their own by the time a puppy is about 12 weeks of age. Otherwise, surgery is the best treatment. With effective surgical intervention, the prognosis for an uncomplicated inguinal hernia is excellent. If the hernia has become trapped (entrapped) or strangulated, the prognosis is more guarded (uncertain) and depends on the degree of organ damage that occurred before surgery.

How can I prevent an inguinal hernia in my dog?

Having your female dog spayed (ovariohysterectomy) will decrease circulating estrogen, reducing the chances of tissue breakdown in the inguinal ring area and thus reducing the risk of an inguinal hernia. Maintaining a healthy body weight may also reduce the risk of this condition occurring. It is best to neuter non-breeding male dogs as well. Intact male dogs with congenital inguinal hernias should not be bred due to the potential for passing this condition to their offspring.