What Is a Perineal Hernia?
A perineal hernia happens when the muscles of the pelvic diaphragm, the sling of muscle on either side of the anus, weaken and separate. Fat, fluid, part of the rectum, and sometimes the bladder or prostate can then push backward through the gap and sit under the skin beside the tail. The result is a soft swelling next to the anus, usually on one side but sometimes both.
It is overwhelmingly a condition of middle-aged and older intact (unneutered) male dogs. It is rare in females and uncommon in cats, where it usually follows chronic constipation or urinary surgery.
Why intact males?
Male hormones and an enlarged prostate are thought to weaken the pelvic muscles, and the straining an enlarged prostate causes makes it worse. Neutering is part of both treatment and prevention.
Risk Factors
- Intact males aged 7 and older
- Breeds: Boston Terriers, Boxers, Collies, Corgis, Dachshunds, Pekingese, Old English Sheepdogs and mixed breeds with short tails
- Chronic straining: prostate enlargement, long-term constipation, diarrhea or anal gland problems
Signs to Watch For
- A soft bulge on one or both sides of the anus that may come and go
- Straining to pass stool, or passing small, flat or ribbon-like stools
- Constipation or stool that collects in a pouch of the rectum
- Licking or discomfort around the tail base
- Straining to urinate or producing little or no urine
Emergency red flag
If your dog strains to pee and nothing comes out, or vomits and seems painful, the bladder may be trapped in the hernia. This can cause kidney failure within a day. Go to an emergency vet immediately.
Diagnosis
Most perineal hernias are found on a rectal exam: your vet feels the gap in the muscle wall and the pouch where stool collects. Ultrasound or X-rays show whether the bladder, prostate or intestine has moved into the hernia, and blood work checks kidney function and anesthetic fitness.
Treatment
- Surgery: the definitive fix. The surgeon closes the gap, often by moving a nearby muscle (the internal obturator transposition) or using mesh. Both sides may be repaired if both are weak.
- Neutering at the same time: strongly recommended, since it shrinks the prostate and lowers the chance of the hernia returning.
- Medical management: stool softeners, a high-fiber diet and occasional manual emptying of the rectum can buy time but do not fix the hernia, and the risk of bladder trapping remains.
Recovery and Outlook
Most dogs recover well after surgery, with recurrence rates commonly reported in the range of 10 to 20 percent, lower when the dog is neutered. Expect a cone, pain relief, stool softeners and leash-only walks for 2 to 4 weeks. Infection at the incision and temporary straining are the most common complications.
Prevention
Neutering male dogs that are not intended for breeding is the most effective prevention; see our guide to dog neutering. Keeping stools soft and regular and treating prostate or anal gland problems early also reduces straining.
Frequently Asked Questions
Can a perineal hernia go away on its own?
No. The muscle gap does not heal by itself, and it usually gets larger over time. Diet changes only manage symptoms.
Is a perineal hernia an emergency?
Not always, but it becomes one if your dog cannot urinate, is vomiting, or the swelling is suddenly larger and painful.
Do cats get perineal hernias?
Rarely. When they do, it is usually linked to chronic constipation or previous urinary surgery. See hernias in cats.
Noticed a swelling beside your dog’s tail? Find a veterinary clinic near you for an exam.