Perineal Hernia in Dogs
On each side of the anus, muscles close off the back of the pelvis and support the rectum. In a perineal hernia, these muscles weaken and separate: fat, the rectum, and sometimes the prostate, bladder, or a loop of intestine slip under the...
What is it?
On each side of the anus, muscles close off the back of the pelvis and support the rectum. In a perineal hernia, these muscles weaken and separate: fat, the rectum, and sometimes the prostate, bladder, or a loop of intestine slip under the skin.
A soft swelling, usually with little or no pain, then appears under the tail, on one side of the anus or both. The deformed rectum traps stool: the dog strains for long periods and becomes constipated.
The condition most commonly affects intact adult or senior male dogs. It typically develops gradually and is not urgent, except when the bladder becomes trapped in the hernia: the dog can then no longer urinate.
Key point
A dog that cannot urinate or strains without passing urine should be seen urgently: the bladder may be trapped in the hernia.
Commonly observed signs
These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.
Related signs — each one links to its page:
Soft swelling under the tail, beside the anus, on one side or both; the skin over it is normal, with no wounds.
The swelling may enlarge when the dog strains and shrink at rest.
Prolonged straining to defecate, pain during bowel movements, constipation.
Stool that remains stuck, sometimes flattened or passed in small amounts.
Difficulty urinating, small amounts of urine, straining without result when the bladder or prostate are displaced into the hernia.
In cases of complications: lethargy, vomiting, swelling that has become firm and painful.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
Weakening of the muscles that close off the back of the pelvis is the direct cause; the reason why these muscles weaken is not completely understood.
Male hormones appear to play a role, which explains why intact males are most affected.
Repeated straining, from chronic constipation or prostate disease, promotes hernia development.
Intact males: by far the most commonly affected dogs; females are rarely affected.
Middle-aged or senior dogs.
Mixed breeds as well as purebreds; breeds mentioned include the Welsh Corgi, Boston Terrier, Boxer, Collie, Kelpie, Dachshund, Miniature Poodle, Old English Sheepdog, and Pekingese.
Prostate disease.
Chronic constipation or prolonged straining.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
The veterinarian examines the area around the anus and performs a rectal examination, feeling for muscle weakness and the pouch formed by the hernia.
The veterinarian checks whether the dog is urinating normally. If your dog cannot urinate, the bladder is emptied and repositioned as an emergency procedure.
Ultrasound or X-rays show what is inside the hernia: fat, rectum, prostate, bladder, or intestine.
The prostate is examined, since prostate disease is often associated with this condition.
A blood test assesses kidney function, especially if the dog had difficulty urinating.
Treatment
Long-term treatment is surgical: the surgeon closes the gap between the muscles to reposition the organs and support the rectum.
Castration is often performed at the same time in intact males, especially to treat an enlarged prostate.
While awaiting surgery, or when surgery is not possible, your veterinarian may recommend a suitable diet and products that soften stools, and may empty the rectum if needed. These measures provide relief but do not repair the hernia.
A dog that cannot urinate is treated urgently before any other intervention.
Do not attempt to push the lump back yourself or give an enema without veterinary advice.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
There is no reliable preventive measure.
Castration in male dogs is a preventive option to discuss with your veterinarian, particularly in dogs with prostate problems.
Have constipation treated promptly if it persists or if your dog repeatedly strains to pass stools or urine.
In older intact males, the annual veterinary check that includes a rectal examination allows early detection of muscle weakness before a lump develops.
Possible complications
Urinary obstruction when the bladder becomes trapped in the hernia: without prompt treatment, the kidneys can suffer severe damage.
Strangulation of a section of intestine, which loses its blood supply: a life-threatening emergency.
Worsening constipation, with progressive distension of the rectum.
Recurrence, sometimes on the opposite side.
Following surgery, as with any procedure in this area, infection of the incision or temporary difficulty controlling bowel movements.
When to see a veterinarian
Your dog cannot urinate or strains to urinate with no urine being passed: seek emergency care.
The lump becomes hard and painful, or your dog is lethargic or vomiting: seek emergency care.
Your dog has not passed stool for several days despite straining: consult your veterinarian during business hours.
You notice a soft lump under the tail, beside the anus, even if it does not seem to cause pain.
Your dog strains for prolonged periods or experiences pain when defecating, or frequently has constipation.
Prognosis
Once repaired surgically, a perineal hernia generally heals well: most dogs return to normal bowel movements.
Recurrence is possible, especially if the underlying cause of straining persists.
The outlook is more guarded when the bladder or bowel was trapped for a prolonged period before treatment.
Frequently asked questions
A lump next to the anus: hernia or anal sac abscess?
A hernia forms a soft swelling, usually not very painful, beneath normal skin; it mainly affects the older intact male. An abscess of the anal sacs is hot, reddish-violet, and very painful, appears within a few days, and may rupture. A hard swelling in a dog that drinks a lot should prompt you to look for a tumor. In any case, consult your veterinarian.
Why can't my dog urinate anymore?
The bladder may slide into the hernia and become kinked, blocking urine flow. This is an emergency: without prompt treatment, the kidneys can be damaged. Seek medical attention immediately.
Is castration necessary?
It is often proposed at the time of surgery, especially when the prostate is enlarged. In an intact male, it can also be discussed with the veterinarian as a preventive measure. The decision is made with him, depending on the age and condition of the dog.
Can diet alone be sufficient?
Appropriate diet and softer stools relieve the dog's discomfort, but do not close the hernia. They serve to buy time while awaiting surgery or to help a dog that cannot be operated on, under veterinary supervision.
References
Content reviewed by the TunisieVet editorial team · Updated 11 October 2026
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