Neutering is an important aspect of preventative healthcare that most owners will consider. Vets recommend castration in male dogs and cats to stop their reproductive abilities, as well as reduce and prevent multiple health and behavioural issues. You may be wondering if there are any alternatives to castration. For example, can we vasectomise our canine and feline companions like in humans? Read on to find out more about how a vasectomy is done and why we don’t generally recommend it as a substitute for castration. 

How is a vasectomy performed?

A vasectomy involves tying off and resecting a small section of the ductus deferens. The ductus deferens is the tube through which sperm travels from the testes to the opening of the penis during ejaculation. By doing this, we remove the dog or cat’s ability to reproduce. It’s important to keep in mind that they do not become immediately infertile after the procedure. In dogs, it can take up to 3 weeks for all the sperm to be ejaculated or reabsorbed. Whereas in cats, it can take up to 7 weeks. Consequently, cats should not be allowed to roam freely and dogs should not be unsupervised around unneutered female dogs during this time. 

Why is the procedure not commonly performed?

Vasectomising dogs and cats is not something that is carried out routinely. Unlike surgical castration, the testes are not removed. As a result, the procedure only inhibits fertility and has no impact on the production of testosterone. This means they retain intact male behaviours and are at risk of developing hormonally associated diseases. 

(As an aside, castration is 100% effective, and cannot reverse itself if carried out correctly. Even in humans, about 1 in 2000 patients will spontaneously reverse the process, with the divided ductus deferens fusing and reopening – (Editor).

What behaviours will vasectomised dogs and cats maintain?

Vasectomised dogs and cats will continue to exhibit any testosterone-driven behaviours that they did when they were still intact. This may include:

  • Desire to roam and seek out intact female dogs or cats 
  • Aggression, especially towards other male dogs or cats
  • Urine marking and spraying
  • Humping or mounting

Which hormonally associated problems are vasectomised cats still at risk of developing?

Vasectomised cats, like their unneutered counterparts, are much more likely to have the compulsion to fight, which can lead to some nasty problems. They may fight to compete for female cats, to defend their territory or to assert their dominance. Wounds that break the skin surface can develop into cat bite abscesses and these may need to be lanced and treated with anti-inflammatories and antibiotics. 

Fighting also increases cats’ risk of becoming exposed to and infected with feline immunodeficiency virus (FIV, aka cat AIDS) and feline leukaemia virus (FeLV). Both of these diseases are spread through cat bites and are contagious and incurable. Furthermore, the testosterone-fuelled desire to roam far and wide in search of a mate makes uncastrated cats more susceptible to road traffic accidents which can leave them with fatal injuries. 

Which medical conditions are vasectomised dogs still at risk of developing?

Testicular tumours 

While castrated dogs benefit from having the risk of testicular cancers completely removed, vasectomised dogs do not. Testicular tumours are common in older dogs. Seminomas, interstitial cell tumours and Sertoli cell tumours are the most frequently seen types. 

Benign prostatic hyperplasia

Benign prostatic hyperplasia is the most common prostatic disease in older dogs, whereby the prostate gland becomes abnormally enlarged. The condition is linked to testosterone, which facilitates the growth in number and size of prostatic cells. Many dogs with BPH are asymptomatic but some may show clinical signs such as difficulty urinating, straining to defecate, blood in urine and ribbon-like faeces. 

Perianal adenoma

Perianal adenoma is a cancer of the sebaceous glands located in the skin around the anus. It is the most common perianal tumour in older male dogs and its development is thought to be dependent on testosterone. The tumours are benign and slow-growing and may appear as single or multiple lumps. These masses can ulcerate and become infected.

Perineal hernia

Perineal hernias arise when there is weakening of the muscles of the pelvic diaphragm. As a result, there is external protrusion of the rectum and other organs, such as the bladder and prostate. The condition has multiple risk factors, including hormonal imbalances and enlarged prostate glands. Some signs that may be seen are difficulty or pain on defecating, constipation and perineal swelling.

With all the above conditions, castration is indicated, either as the treatment of choice or as concurrent therapy. 


Vets recommend castration not only as a means of population control but also for the medical and behavioural benefits that it brings. However, vasectomies can only inhibit reproductive ability. In cats, the procedure will not remove any hormonally fuelled behaviours, which increases their risk of contracting infectious diseases. And in dogs, they will not be protected from the reduced risks of developing testicular and perianal tumours, prostate issues and perineal hernias. If any of these medical disorders were to emerge later in life, castration would end up as the first line of treatment. 

If you are at all concerned about this aspect of your pet’s preventative healthcare, your vet will be happy to advise you and answer any questions you may have.

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