Male dogs are often described as “slowing down” in middle age. Sometimes the explanation is the prostate. Benign prostatic hyperplasia is a non-cancerous enlargement driven by testosterone, it is the most common prostate problem in dogs, and it develops almost exclusively in dogs that are still entire.
What the Prostate Does, and Why It Grows
The prostate is a small gland that sits around the urethra near the neck of the bladder and contributes fluid to semen. Testosterone is converted in the body into dihydrotestosterone, which stimulates the glandular tissue to multiply. Because the trigger is cumulative hormone exposure rather than a single event, the odds climb steadily with age. Roughly half of entire male dogs have microscopic evidence of the condition by four to five years old, and more than ninety per cent by eight to nine. Neutered dogs are essentially spared. The important exception is prostate cancer, which is not hormone-driven and is in fact seen more often in neutered males.
Signs Most Owners Put Down to Age
- Straining to pass stool, or stools that come out flat and ribbon-like, because the enlarged gland presses on the rectum.
- Blood in the urine, or a blood-tinged discharge from the penis that is unrelated to urinating.
- Passing urine more often in smaller amounts, or dribbling.
- Constipation that comes and goes.
- Reduced fertility in a stud dog.
- Nothing at all, with the enlargement found during a routine rectal examination.
Why Your Vet Will Not Stop at “Big Prostate”
Enlargement is a finding, not a diagnosis. The look-alikes matter because their treatments are completely different. Prostatitis, an infection of the gland, is the one to catch early: it can be painful, cause fever and lethargy, and it needs weeks of antibiotics, sometimes with hospitalisation. Prostatic cysts and abscesses are also possible, and prostate cancer, though uncommon, is serious and often advanced by the time it is found. Expect a rectal examination, an ultrasound to measure the gland and look at its texture, urinalysis with culture, and sometimes sampling of prostatic fluid or a biopsy. A blood test for canine prostate-specific arginine esterase can support the suspicion of benign enlargement, but it cannot rule out infection.
What Actually Shrinks the Prostate
For a dog that is not part of a breeding programme, castration is both the treatment and the prevention. The prostate begins to shrink within weeks and typically returns to near-normal size in about three to four months, and most signs resolve with it. For a valuable stud dog, options that block testosterone — a five-alpha-reductase inhibitor such as finasteride, or a slow-release implant — can reduce gland size while preserving fertility, but the prostate re-enlarges within months of stopping. Dogs that are straining may also need stool softeners while the gland shrinks. What is not a plan is watching and waiting: untreated enlargement predisposes dogs to infection and, over time, to painful complications, and the earlier the cause is identified the more options remain open. This is also why a rectal examination belongs in every senior wellness check for an entire male dog, even when the owner reports no problems at all.
An enlarged prostate is usually manageable, but only once you know what is causing it. If your entire male dog is straining, dribbling or slowing down, ask for a rectal examination and an ultrasound rather than assuming it is simply age. And if he is not needed for breeding, castration remains the simplest long-term answer.