Perineal hernias result from weakening or complete failure of the muscular diaphragm of the pelvis. Normally, the pelvic diaphragm allows for rectal support and keeps the abdominal contents from encroaching on the rectum. Pets with perineal hernias will demonstrate a swelling adjacent to the rectum on one or both sides coupled with signs of constipation, difficulty defacating, lethargy, difficulty urinating, and altered tail carriage.
The underlying cause for weakening or failure of the pelvic diaphragm is unclear at this time. However, many theories are proposed, all of which may be working separately or in unison to allow for pelvic diaphragm weakening or failure. The disease primarily affects older pets, usually between the ages of 7 to 9 years. Non-castrated male dogs and cats are also over-represented.
Pets with perineal hernias typically demonstrate a swelling adjacent to the anus on one or both sides (Figure 1). The swelling may contain herniated abdominal and pelvic canal contents, such as a dilated rectum, prostate, urinary bladder, fat, omentum, and small intestine. Clinical signs seen in pets with perineal hernias are related to the organs entrapped in the hernia. Typically, these signs include:
- straining to defecate
- straining to urinate
- inability to urinate
- urinary incontinence
- abdominal pain
- altered tail carriage
To diagnose perineal hernia your veterinarian will perform a thorough rectal examination. This will help to determine the presence or absence of a mass-like lesion, prostate disease, contents of the hernia, and to determine unilateral or bilateral disease. Some patients may require analgesic or sedative administration for completion of a rectal exam. Once the diagnosis of perineal hernia has been made, a thorough metabolic and abdominal work-up should be instituted. Your primary care veterinarian will likely recommend a complete blood count, biochemical profile, and urinalysis to determine any concurrent systemic illness. Advanced diagnostic imaging (ultrasound and abdominal radiographs) may be recommended to help determine hernia contents, bladder position and size, colon position and size, prostate disease, or the presence of cancer (Figure 2).
Patients demonstrating any swelling adjacent to the rectum along with the clinical signs mentioned above should seek veterinary advice as soon as possible. Organ entrapment into the perineal hernia may be life threatening and necessitate emergency stabilization prior to definitive surgical intervention. Your veterinarian may wish to refer you and your pet to an ACVS board certified veterinary surgeon for surgical repair of a perineal hernia.
Perineal hernias, by themselves, may cause constipation, which in turn, may damage the motility function of the colon. Perineal hernias may also disrupt your pet’s ability to urinate. Occasionally excessive straining may cause the urinary bladder to retroflex (flip over backwards into the pelvic canal) leading to urinary obstruction and potentially loss of blood supply to the bladder. Entrapment of a loop of intestine into the hernia may cause significant pain and loss of the blood supply. Emergency surgery is indicated for pets with signs of abdominal pain, inability to urinate, and a strangulated loop of small intestine.
After surgery, your pet may be placed on a broad-spectrum antibiotic. All patients will receive pain medications to reduce their post-operative discomfort. Dietary modification with a high fiber diet coupled with stool softeners are sometimes used to help with reducing the pain and straining associated with defecation. In addition, it helps to reduce the potential for breakdown of the repaired tissue. Your pet should be kept calm and quiet for the first two weeks after surgery to allow for tissue healing. Elizabethan collars are warranted to prevent patient damage to the surgical repair. Cold compresses applied to the surgical site may be recommended to help diminish swelling and perineal irritation.
The prognosis is good for the majority of cases; however, in 10-15% of the cases, recurrence of the hernia may occur within a year. Prevention of over activity and self-trauma may help lower this recurrence rate.
There is no proven means to prevent perineal hernias from forming. The problem is rarely seen in castrated male dogs so early castration in dogs not intended for breeding purposes is recommended.