Castration, or surgical removal of the testicles, is one of the most common veterinary procedures for male dogs. Castration is widely recommended for most non-breeding male dogs to prevent unwanted pregnancy in intact females; prevent diseases such as prostate enlargement and testicular cancer; and to minimise certain behaviours. We always encourage you to ask your vet questions first, but we thought it would be a good idea to outline how a typical dog castration happens. Bear in mind that every veterinary practice will have different protocols and techniques, so the following may not apply to every individual surgery. 

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Booking In

Vet practices are busy places, so you will need to pre-book your dog’s castration. This is easily done in person, by ringing up reception or booking online. The age at which dogs can be first castrated varies based on your dog’s breed and size; so please ask your vet the appropriate age for your dog. There is generally no upper age limit provided they are otherwise healthy. Many vets also offer a deslorelin hormone implant for male dogs, which temporarily renders them infertile and prevents production of testosterone. A deslorelin implant is a good alternative for owners unsure how their dog may react to surgery, or for dogs where castration is not practical. 

Pre-Operative Period

Once your dog’s castration has been booked, you will receive pre-operative instructions. It is important you read these thoroughly. It will explain the procedure and what you need to do to prepare in advance. 

The most important step is ensuring your dog has been starved appropriately (up to 12 hours, depending on the anaesthetic protocol) before surgery. The recommended length of time varies depending on the individual dog. This is advised to prevent vomiting under anaesthetic. If a dog vomits under a GA, he may breathe the vomit into his lungs. This can result in serious post-operative complications. If you have any doubt that your dog has been starved before the procedure it is safer to delay and rebook later. Water can be given as normal unless otherwise advised. 

A pre-operative blood test may also be advised, particularly for older dogs or those with health conditions. These are performed to check that your pet’s organs are functioning properly, in particular the liver and kidneys. Any problems with your pet’s organs may affect the drugs given or even delay surgery. Specialist blood tests, such as checking your pet’s blood clotting function, may be recommended depending on the breed. 

Certain dogs with brachycephalic (short-nosed) faces may also be advised to start antacid medication a few days before the procedure. These dogs are at a much higher risk of vomiting under GA, so antacids will help reduce this risk. 

Finally, it is recommended that dogs are bathed or at least brushed clean on their undersides before the operation. This will make surgical cleaning quicker and reduce the time they spend under general anaesthetic. Dogs should also have a short walk on the morning of the operation to reduce their energy level and allow them to urinate and defaecate. 

Admission

On the day of surgery your dog will be admitted by a vet surgeon or vet nurse. This will involve a clinical exam (particularly if this has not been done recently) to check they are healthy that day, and confirming they have been pre-starved (as appropriate). The staff member will then go through the consent form. This is a legal document so it is important you listen and read carefully. The form details the surgery itself, the risks involved, estimate of costs, possible complications and post-operative management. It will also have your contact details. It is critical that you provide an up to date contact number and you are available for the day in case there is an emergency.

Once this has been signed and dated, and you are happy with the plan for the day, you can give your dog a hug goodbye and the staff member will take them through to the kennel area to get settled. If you would like you can leave some treats, soft toys or a blanket for your dog for comfort after their surgery. 

Some vets will ask for a deposit or full payment for the surgery in advance; others will ask you to pay at the end – have a quick check with reception before you leave. 

Preparing for Surgery

Now your dog is in practice he can start being prepared for surgery. If a pre-operative blood test has not already been performed but has been recommended, it will be done now. The vets or nurses may also fit an intravenous catheter and connect your dog up to intravenous fluids if these are recommended too. Intravenous fluids help maintain a dog’s blood pressure under anaesthetic. 

Most dogs will then receive a pre-medication, given intravenously or intramuscularly. These are drugs that provide pain-relief, sedation and anxiety-relief to help keep your dog as comfy as possible before and during surgery. The drugs vary wildly depending on the case, practice, and individual vet. Common drugs used are medetomidine, acepromazine, buprenorphine and methadone.  

Induction of Anaesthesia

Once the pre-medication kicks in (this can take anywhere from 5 to 45 minutes depending on the drugs used), the dog can be fully anaesthetised and surgery can begin. From this point, there are always at least two people present for safety, often the operating vet surgeon and assisting vet nurse. Induction of anaesthesia is mostly done via intravenous anaesthetic drugs, commonly propofol or alfaxalone. This takes a few seconds. 

After anaesthesia has been induced, an endotracheal tube is placed into your dog’s airways to provide oxygen and inhaled anaesthetic gases (isoflurane or sevoflurane) during the surgery. In some rare cases, anaesthesia may instead be maintained with a steady flow of intravenous drugs, such as propofol. The team will spend a few moments ensuring your dog is under the correct plane of anaesthesia – not too deep and not too light.

Now he has settled, your dog will be prepared for surgery

He will have his fur shaved off around the surgical site. This is most commonly just in front of the scrotum, over the penis. A larger patch of fur will be shaved off than the incision. This is to ensure the surgical site can be sterilised properly. The shaved area is cleaned then surgically cleaned with antiseptic solution.

At some point during preparation, local anaesthetic may be applied under your dog’s skin where the incision will be, or even directly into the testicles. This provides further pain relief and comfort during and after surgery. Common agents used are lidocaine or bupivacaine. A subcutaneous injection of a non-steroidal pain relief drug such as meloxicam, carprofen or robenacoxib is often given now too. 

During this period, the vet will be surgically sterilising their hands, and may wear sterile clothing too. Once your dog is prepped they are moved into theatre (is it safer to prepare the dog in another non-sterile room to keep theatre as clean as possible).

Surgery

Your dog is placed on the operating table on their back. Some dogs may have to lie in cradles if they don’t balance well on their back. The vet nurse will take a few moments to ensure your dog has settled under anaesthesia again, and will then open the vet’s surgical equipment. A sterile drape is placed over the surgical field to minimise contamination from the non-sterile area. During surgery, the nurse will constantly monitor your pet’s depth of anaesthesia, breathing and heart rates, temperature, blood pressure, ECG and more, making adjustments where necessary. 

Most surgeries begin with the vet cutting into your dog’s skin with a sharp scalpel blade. They then dissect the subcutaneous fat to reach the testicles, which are pushed up towards the penis so they sit under the surgical site (pre-scrotal) then pushed out of the incision hole. The vet will then either remove the testicles and enclosing tunic together (closed castration) or cut through the tunic to the testicle to provide better access to the spermatic cord (open castration). 

Regardless, the vas deferens and testicular arteries and veins are all clamped with haemostats (a special type of clamp). One or more ligatures are tied below the haemostats to stop bleeding, then the cord is cut allowing removal of the testicle. If the outer tunic has been separated from the testicle first (open castration), the vet may opt to close the hole in the tunic (open modified castration). This process is repeated with the other testicle, and the vet checks for any bleeding. In almost all cases, both testicles will be removed through the same incision, so you will only see one surgical wound.

The major exception to this process is retained testicles

Testicles that have not fully descended into the scrotum (which usually happens before 14 days old – and almost always by 6 months) require a more complicated procedure. For these testicles a second incision may be needed to remove it. In cases where the testicle is still within the abdomen, the abdomen must be opened to locate and remove the testicle. 

Once both testicles are removed, the incision(s) are closed using suture material

This is generally done in two layers, the subcutaneous fat and the skin (the muscle layer will also need to be closed if the abdomen has been opened). Internal sutures are dissolvable and will break-down over time. The skin may be closed with dissolvable intra-dermal sutures, non-dissolvable sutures that are removed a week or two post-operatively, or surgical staples. Tissue glue (surgical superglue) may also be used in some cases. A dressing may be applied on top of the wound.

Waking Up and Monitoring

Now surgery has ended, the dog’s anaesthetic gases are stopped and the dog will slowly start to wake up. They will remain on oxygen breathing via the ET tube until they are completely awake for safety. When they wake, they are moved back to kennels for monitoring. The post-anaesthetic period is a risky time for all animals, so a nurse will check them regularly to ensure they are safe. They may regularly check your dog’s heart and breathing rate, the surgical site, temperature and pain level. More pain relief may be given if they feel the dog is still painful. Intravenous fluid therapy may be continued until discharge, or stopped now. 

It normally takes a few hours before your dog is ready to go home, so someone will ring you to let you know your dog is out of surgery and to organise a time for collection. Your pet’s intravenous cannula (catheter) will be removed and the site covered with a bandage before discharge. 

It is important that your dog does not lick or scratch his wound post-operatively. So a buster collar or pet shirt are often put on them now while they are still sleepy. 

Discharge and Post-Operative Period

Once awake, you are invited back to the practice and your dog is discharged. The vet or vet nurse discharging will discuss post-operative management. 

Your pet will be sleepy for the first evening, and they may not want to eat

This is normal, and they should be brighter by the next day. Rarely, they may vomit once, which is also normal – a bland diet given little and often can help minimise this. The wound must be protected, so keep the buster collar or pet shirt on at all times. Licking the wound could lead to wound breakdown, infection and further complications. 

Check the wound every day

In the first few days there may be a little bloody oozing, but it should be mild. Redness and clipper rash, and a swollen scrotum are also common. Look out for significant bleeding or discharge, signs of infection or bad smell, loose sutures or wound breakdown. If you see any of these issues, or your dog seems distressed, painful, off food or overly quiet, let your vet know as soon as possible. 

Most dogs will go home with post-operative pain relief

These are commonly oral anti-inflammatories, but paracetamol, tramadol or other drugs may also be used. Even if your dog does not seem painful, only stop once your vet says it is appropriate to do so. Antibiotics are very rarely given for clean routine surgeries anymore. 

Exercise for the first few days should be reduced – take them on a lead into the garden only, until a vet or nurse has checked the wound. This should take place around 3-5 days post-op. You may also be asked to have one more check at 10-14 days, particularly if sutures or staples need to be removed. Once your dog has been seen, normal exercise can slowly be reintroduced until around 2 weeks post-op. At this point most dogs will have healed and can be treated as normal. 

Remember, they won’t be infertile immediately…

Finally, there is a theoretical chance that male dogs remain fertile for around 6-8 weeks post-castration. Sperm are stored further up the reproductive tract and some may well survive the procedure, thus it is recommended to keep them away from intact female dogs for this period. Male dogs are also more prone to weight gain post-castration, so reducing their food intake is sensible. 

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