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PERINEAL HERNIAS IN THE DOG AND CAT
Overview
Perineal hernias result from weakening or complete failure of the muscular diaphragm of the pelvis. Normally, the pelvic diaphragm will allow for rectal support and to keep the abdominal contents from encroaching on the rectum. Patients with perineal hernias will demonstrate a unilateral or bilateral swelling adjacent to the rectum, coupled with signs of constipation, difficulty to urinate and altered tail carriage.
Causes
The underlying cause for weakening or failure of the pelvic diaphragm is unclear at this time. However, many theories are proposed, all which may be working separately or in unison to allow for pelvic diaphragm weakening or failure.
Incidence and Prevalence
There are many factors associated with the development of perineal hernias, such as breed, age and sex. Dog breeds that are over-represented in the veterinary literature include the Boston terrier, Corgi, Boxer, Collie, Kelpie, Old English Sheepdogs, Dachshund and Collie. The disease will primarily affect older animals, usually between the ages of 7 to 9 years. Male dogs and cats that are not castrated are also over-represented. Fortunately, prevalence of the disease process is very low in the dog and extremely low in the cat, representing 0.1 to 0.4% of all cases presented to veterinary clinics.
Signs and Symptoms
Patients with perineal hernias typically demonstrate a unilateral or bilateral swelling adjacent to the anus. (Figure 1) The swelling may contain herniated abdominal and pelvic canal contents, such as a dilated rectum, prostate (male), urinary bladder, fat, and small intestine. Clinical signs seen in patients with perineal hernias are related to the organ entrapped in the hernia. Typically these signs consist of constipation, straining to defecate, straining to urinate, inability to urinate, urinary incontinence and altered tail carriage.
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Figure 1. A large perineal hernia in a dog.
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Risk Factors
Risk factors for developing perineal hernias include species, age, sex and reproductive status. Perineal hernias are most common in intact male dogs, which are usually diagnosed between 7 and 9 years of age.
When to Seek Veterinary Surgical Advice
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 regular veterinarian may wish to refer you to a surgical specialist for surgery to repair a perineal hernia. To find an ACVS veterinary surgeon in your area, click here: Search for a Surgeon
Exam, Screening Tests and Imaging
Once the diagnosis of perineal hernia has been made, a thorough metabolic and abdominal work-up should be instituted. A complete blood count, biochemical profile and urinalysis should be performed to determine any concurrent systemic illness. A thorough rectal examination should be completed to determine the presence or absence of a mass-like lesion, prostate disease, contents of the hernia and to determine unilateral vs. bilateral disease. 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 neoplasia (cancer).
Differential Diagnoses
Differential diagnosis for perineal swelling must include the following:
- perineal hernias
- perineal neoplasia (cancer)
- rectal neoplasia
- mega-colon
- rectal prolapse
- anal sacculitis (infection in the anal sacs)
- anal sac abscess
- anal sac neoplasia
- trauma
Differential diagnosis for clinical signs consistent with constipation, i.e., straining to defecate and fecal incontinence includes:
- perineal hernias
- prostatitis
- prostatic abscess
- prostatic cyst/pseudocyst
- lumbosacral disease
- intervertebral disk disease
- dysautonomia
- degenerative myelopathy
- rectal neoplasia
- pelvic trauma/fractures
- anal sacculitis
- anal sac abscess
- anal sac neoplasia
For clinical signs associated with straining to urinate, including difficulty urinating, inability to urinate or urinary incontinence, the differential diagnosis would include:
- prostatitis
- prostatic abscess
- prostatic neoplasia
- prostatic cysts/pseudocysts
- rectal/colon neoplasia
- bladder neoplasia
- bladder/urethral stones (calculi)
- congenital abnormalities
- neurological diseases
- perineal hernias
Complications Caused by Disease
Perineal hernias, by themselves, may cause constipation, which in turn, may damage the motility function of the colon. Clinical signs consistent with urinary tract dysfunction should be addressed immediately, due to the fact that metabolic wastes cannot be properly eliminated from the body, which can affect the immediate health of the patient. Occasionally the excessive straining caused by the hernia, causes the urinary bladder to retroflex (flip over backwards into the pelvic canal) causing urinary obstruction and potentially loss of blood supply to the bladder. This can be a potentially fatal complication. Entrapment of a loop of intestine may also create a surgical emergency.
Treatment Options
Treatment of perineal hernia may consist of either medical or surgical therapy. Medical therapy is indicated for preparing a patient for surgery but is generally unsuccessful at permanently controlling clinical signs associated with the disease process. Medical management will consist of a combination of enemas, stool softeners, IV fluid therapy, dietary management and analgesics. Surgery is aimed at repairing the pelvic diaphragm and potentially suturing or tacking the colon and the bladder to the abdominal wall to help prevent reoccurrence and colon or bladder entrapment. The surgery may involve placing sutures to restore the pelvic diaphragm, or a surgical mesh may be implanted. In severe hernias, it may be necessary to transfer a flap of muscle from one of the rear legs to aid in closure of the hernia defect. It is recommended that all patients be castrated during the surgical procedure to help decrease the risk of reoccurrence. Some surgeons will do a bilateral hernia repair at the same time, while others prefer to wait 4-6 weeks before performing the second herniorrhaphy in dogs with bilateral disease.
Potential Complications
Complications from surgery are low and include:
- incisional swelling
- drainage
- infection
- fecal incontinence
- straining to defecate
- rectal prolapse
- recurrence of the hernia or failure of the primary repair
- urinary tract dysfunction
- sciatic nerve paralysis
During initial hospitalization, all patients are monitored for complications. Should complications arise, medical or surgical intervention may be required.
Aftercare
After surgery, most patients will 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 and to reduce the potential for breakdown of the repaired tissue. The patient should be kept calm and quiet for the first two weeks after surgery to allow for tissue healing. Warm compresses applied to the surgical site may be recommended to help diminish swelling and perineal irritation.
Prognosis
The prognosis is good for the majority of cases seen by a veterinary surgeon, however, recurrence of the hernia may occur within a year in 10-15% of the cases.
Prevention
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.
—Roy Barnes, DVM
Small Animal Resident
Editor: William Daly, DVM
Diplomate ACVS
Posted 8/13/2004
The American College of Veterinary Surgeons (ACVS) recommends contacting an ACVS Board Certified Veterinary Surgeon or your general veterinarian for more information about this topic. Search for an ACVS Veterinary Surgeon
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