When talking about neutering, vets often list a series of diseases that neutering can help prevent. Prostate disease is often near the top of that list – but is it true? What are the impacts of neutering on prostate disease in dogs? Our vet blogger Sian has been digging into the science in this, the first of our “Neutering Week” posts.
What is the prostate gland in dogs?
The prostate is a gland in the abdomen of the male dog. It is an accessory sex gland as it produces seminal fluid. This fluid mixes with sperm produced by the testicles to make semen. The fluid passes into the urethra, the tube that joins the bladder to the penis. The prostate surrounds the urethra and sits above the urinary bladder and below the rectum.
Neutering of the male dog usually means surgical castration. Both testicles are removed in this procedure. Hormone treatments can be used to chemically castrate a dog but these treatments must be repeated to prevent testosterone production as the testicles are not removed.
What does the research say?
Dogs that have not been castrated are called entire or intact. A 2018 article on prostatic disease in the dog explained that all intact dogs over 6 years old develop a condition called Benign Prostatic Hypertrophy (BPH) (1). BPH causes enlargement of the prostate gland. As the name suggests it is a benign condition in that it does not cause life threatening disease. However, it can make the dog extremely uncomfortable and affect urination and defecation.
What are the signs of BPH?
As the prostate gland enlarges it compresses the urethra. This makes it difficult for the dog to urinate normally. They strain to pass urine, often passing small amounts of urine with great effort. The urine may contain blood or drops of blood may be seen around urination because of the straining. Fortunately, complete obstruction of the bladder is rare.
A significant increase in size of the prostate gland also causes compression of the rectum. This causes difficulty passing faeces, the dog will become constipated and produce small amounts of flattened faeces.
Why does BPH happen?
BPH occurs because of testosterone production by the testicles so castration prevents it. Castration is used to treat BPH as testosterone levels fall, the prostate shrinks. The symptoms of discomfort and difficulty toileting resolve completely within one month after castration.
Are there any other diseases linked to the dog’s prostate?
BPH increases the risk of other prostatic diseases which cause further enlargement of the prostate gland and more severe disease (2). Therefore, neutering will prevent the prostatic diseases discussed below. Both prostatic cysts and abscesses may require surgery in addition but castration will prevent recurrence.
This is inflammation of the prostate gland. This is usually caused by bacterial infection originating either in the prostate itself, the kidneys or bladder. BPH makes the prostate gland more susceptible to infection as structural changes block ducts within the gland and cause pockets of fluid to accumulate.
Bacterial prostatitis may cause prostatic abscessation, where blocked ducts result in large pockets of fluid. These abscesses become walled off from the body preventing antibiotic penetration and successful treatment. Prostatic abscesses require long antibiotic courses of at least 4 weeks and may require surgery.
These fluid-filled pockets can develop independently or more commonly because of BPH, cancer or inflammation. They are sterile accumulations of fluid occurring within the prostate gland. These cause similar symptoms to BPH: difficulty toileting, abdominal pain and blood in the urine. Prostatic cysts can resolve with castration if they are small but will require surgery if they are large.
Paraprostatic cysts are a little different in that they form because of abnormal tissue attached to the prostate. This tissue is attached to the prostate and secretes fluid causing fluid accumulations next to the prostate. These cysts are sterile but compress the urethra causing discomfort and difficulty urinating. Surgical removal of the cyst is necessary for resolution but castration will usually prevent recurrence. Castration before 4 years of age will usually halt the growth of these cysts as the tissue responds to testosterone.
Squamous metaplasia causes prostatic enlargement due to increased oestrogen. This hormone is secreted in excess by a Sertoli cell tumour of the testicles. As castration involves removal of both testicles, neutering prevents all types of testicular cancer. A common tumour called perianal adenoma also occurs in entire dogs but not castrated dogs as the formation is testosterone dependant.
What about prostate cancer?
There is one prostatic disease which is not prevented by neutering. Prostate cancer is rare in the dog – it is thought to occur in less than 1% of dogs (3) . A study carried out in 2002 (4) showed that castration does not cause prostate cancer but it may favour tumour progression. Therefore, prostate cancer is more commonly seen in castrated dogs than uncastrated dogs. However the incidence is still very low.
Prostate disease occurs in the middle aged to older dog. Testosterone production drives most of the diseases that occur so neutering (castration) will prevent most prostatic diseases. It is important to consider this carefully when your dog is younger as an older dog can have concurrent disease that may make a surgical procedure more complicated.
References and further reading:
2. Niżański W, Levy X, Ochota M, Pasikowska J. Pharmacological treatment for common prostatic conditions in dogs–benign prostatic hyperplasia and prostatitis: an update. Reprod Domest Anim. 2014;49Suppl2:8-15.