Perineal hernia in dogs – symptoms and surgery

Overview

The pelvic diaphragm is a support formed by muscles and connective tissue that keeps pelvic organs in position. Fat or omentum, a fatty tissue fold within the abdomen, most commonly enters the hernia. The bladder, prostate or bowel can also move into it.

The condition is relatively uncommon in dogs. Population prevalence has been estimated at around 0.4%, rather than representing a current rate for every dog population. The hernia is one-sided in 47–66% of affected dogs. Of one-sided hernias, 59–84% are on the right.

A hernia can extend between different muscles beside the rectum, higher up or below the pelvic floor. The same dog may have herniation in several directions or changes on both sides of the pelvis.

Causes

Muscle wasting changes the bowel's position

As the disease progresses, the pelvic support muscles become thin and separate from one another. The levator ani muscle in particular may waste away. With weaker support, the rectum can deviate, bend and dilate.

Long-term constipation and constant straining have been considered possible contributing factors. However, the precise cause of muscle weakening is unknown. Benign prostate enlargement may be associated with hernia development.

Males with a hernia have had larger prostates and more cystic changes than healthy males of the same age. Relaxin leaking from the prostate into surrounding tissues is suspected of contributing to muscle wasting. A direct effect of testosterone or oestradiol on hernia development has not been demonstrated.

Reduced local reflexes may relate to muscles and nerves stretched by the hernia. Nevertheless, not all dogs with an enlarged, cystic prostate develop a hernia.

Risk factors

Around 96–98% of affected dogs are uncastrated males. Ages at onset have ranged from 4–16 years. The usual age at diagnosis is around 7–9 years. Dogs of any size can be affected.

Breed predispositions have been described in Boston Terriers, Boxers, Collies and Dachshunds, for example. Crossbreeds are affected too. Hernias are rare in females and have often been associated with trauma or prolonged coughing.

A female's prolonged cough may result from bronchitis, tracheal collapse or cardiomyopathy, for example. A hernia can also develop in an already castrated male.

Typical symptoms

Signs can fluctuate, making disease onset difficult to date. Among dogs whose owners answered a survey, more than 60% had shown signs for over 3 months before treatment was sought.

• A soft-feeling swelling appears beside or below the anus.

• Your dog strains to defecate but passes little or no faeces.

• Defecation looks painful.

• Urination becomes difficult or attempts are more frequent than usual.

• Urine leaks involuntarily.

• Your dog is subdued and does not want to eat.

• Tail position or carriage changes.

The swelling may also be painless. Some dogs can urinate normally even when the bladder is already in the hernia.

With gradual progression, episodes may become more frequent and severe over time.

Complications and consequences

Urinary retention and bowel strangulation

A bladder displaced backwards can obstruct urine flow and lose its blood supply. A bowel loop trapped in the hernial opening can be damaged when circulation is blocked. Prolonged constipation may also impair colonic movement.

Only 20% of dogs have been described as remaining symptom-free without surgery. During symptomatic treatment, organ strangulation and backward displacement of the bladder remain possible.

Recurrence and postoperative problems

The general reported range for postoperative recurrence is 10–46%. A broader range of 10–50% has also been described with different repair techniques. The proportion experiencing any surgical complication has ranged from 5–68%.

A randomised comparison of 66 males investigated a muscle-elevation technique and a fascia graft. At 12 months, recurrence after muscle elevation was identified in 3/34 dogs, or 8.8%. After fascia grafting, the corresponding proportion was 3/29, or 10.3%.

Possible postoperative problems include wound infection, wound breakdown and temporary pain on defecation. Faecal or urinary continence can also decline. Some dogs retain difficulty defecating even when the repair holds.

Diagnosis at the vet

Rectal examination is central

The vet combines symptom history, external examination and rectal palpation. A finger examination can identify weakened muscle support or an actual hernial opening. Initially, muscles may simply feel thin and lax without an obvious gap.

The examination also assesses rectal position and dilation. Possible tumours and prostate disease are checked at the same time. Both sides are examined because a large hernia can conceal milder changes on the opposite side. Pain relief or sedation may be needed for a successful examination.

A hernia containing the bladder may feel like a firm mass rather than a soft swelling.

Imaging and laboratory tests

Ultrasound helps establish whether the hernia contains the bladder, prostate or a bowel loop. Radiographs may show a faeces-distended rectum and herniated bowel loops containing gas. Blood tests and urinalysis investigate concurrent systemic diseases.

Computed tomography, or CT, can show organs within the bony pelvis in detail. In routine clinical practice, however, rectal palpation is often sufficient for diagnosis and treatment planning.

Where needed, imaging also assesses bladder and colonic size and abnormal prostate changes.

Treatment

Urine flow and general condition are secured first

Urinary obstruction or bowel strangulation requires urgent treatment. The vet can drain the bladder using a catheter or, if necessary, a needle at the practice. A urinary catheter may be left in place to maintain urine flow.

While awaiting surgery, symptoms may be eased with veterinary-selected pain relief and stool-softening treatment. Impacted faeces may need removal from the rectum at the practice. Supportive care alone also suits a dog whose general condition or other diseases prevent surgery.

Surgery reconstructs the missing muscular support

Definitive repair is performed under general anaesthesia. Organs are returned to position and the pelvic support structure is repaired. A common method elevates the internal obturator muscle to support the hernial opening. A tissue graft taken from the thigh fascia is an alternative.

In a recurrent or severe hernia, another muscle flap or mesh may reinforce the repair. Sometimes the bladder or colon is attached to the abdominal wall to prevent renewed backward displacement. Repair choice depends on hernia size, location and previous surgery.

Castration is generally recommended during the same operation for an entire male. Afterwards, the prostate shrinks and pressure on the pelvic support structures decreases. However, not every comparison has found a statistically significant reduction in recurrence risk.

Simply suturing the thin muscle edges together is no longer recommended because of high recurrence risk. A comparison of traditional closure and internal obturator elevation reported recurrence rates of 27% and 11%, respectively.

Collecting a fascia graft requires a separate thigh wound in addition to the hernia wound. For a downward-directed hernia, the semitendinosus muscle at the back of the thigh can be used because it reaches the repair site well. Tissue from the testicular tunic can also be used if the male is still uncastrated.

Surgical mesh can cause a foreign-body reaction or sustain infection. If early weakness is present on the opposite side too, the surgeon may recommend repairing both sides. Concurrent prostate enlargement is also treated where necessary.

Recovery and bowel-function monitoring

Recovery from uncomplicated surgery usually takes around 2 weeks. Mild swelling and pain on defecation may settle with treatment over days or weeks. Diet management and stool-softening medication may still be needed after repair.

Rectal dilation can remain permanent even if bowel deviation is corrected. Ongoing defecation difficulties increase recurrence risk. Another hernia may become apparent even a year after surgery.

Strenuous exercise, running and jumping are usually avoided for the first 2 weeks. Short, quiet lead walks for toileting are permitted. Wound healing and any removable stitches are usually checked after 10–14 days.

Small bruises around the surgical site can be normal and usually fade within around 5–7 days.

Prevention

No completely reliable preventive method is known because the sequence leading to muscle wasting and the disease mechanism remain unclear. An older entire male's health check should include rectal palpation to identify early changes. Early repair of a diagnosed hernia is easier before advanced muscle wasting.

Castration during repair aims to shrink the prostate and reduce recurrence risk. Aftercare that eases faecal passage forms part of recurrence prevention because straining problems can continue after surgery.

Important for dog owners

Record when swelling is visible, how often your dog tries to defecate and whether attempts produce faeces. Monitor the urine stream and unsuccessful attempts separately. Bring details of previous hernia surgery, castration and prostate problems. At discharge, agree which signs require immediate contact and how stool consistency should be monitored.

New or increasing swelling and difficulty defecating need veterinary assessment. Severe pain or hind-leg weakness after surgery may result from a nerve being trapped by a suture.

Do not allow wound licking or chewing; use a protective collar if needed. Wound-edge separation, new discharge or increasing swelling require contact with the veterinary practice. Redness and swelling around the wound should decrease as healing progresses.

An area soiled with faeces can be cleaned with a gentle room-temperature water spray and patted dry with a clean towel. Avoid strongly scented or irritating cleaning products near the wound.

If appetite and alertness do not gradually improve within 2–3 days of discharge, contact the practice for reassessment.

Frequently asked questions

Can a perineal hernia be treated without surgery?

Diet, stool softening and pain relief can ease symptoms but do not repair weakened pelvic support. Supportive care is used while awaiting surgery or when a dog is not fit for an operation. The risk of bladder displacement and organ strangulation remains.

Is a painless swelling harmless?

Not necessarily: a hernia swelling beside the anus is often painless in dogs. Its significance depends on which tissues have moved into it. A trapped bladder or bowel can create an emergency even if the swelling previously caused few symptoms.

Why is a male castrated during hernia surgery?

Castration aims to shrink the prostate and reduce its effects on pelvic support structures. It is generally recommended during hernia repair. However, its effect on recurrence has not been statistically significant in every comparison, so castration does not remove the need for monitoring.

How long does recovery from surgery take?

The usual uncomplicated recovery period is around 2 weeks. Mild local postoperative signs may ease over days or weeks. Defecation problems may persist longer because rectal changes do not always resolve completely even after successful hernia repair.

Can the hernia return after successful surgery?

Yes, and recurrence may become apparent even a year after repair. General recurrence risk has been described as 10–46%. The technique used and previous repair attempts also affect an individual dog's risk. New swelling or straining should be examined by a vet.