In a dog neuter surgery, also called castration, the scrotum (sac containing the testicles) is not usually removed. The incision is made just in front of the scrotum. There are some medical conditions that warrant removal of the scrotal tissue, but that is not the norm.
The most common reason a dog may appear as if the testicles were not removed is because there is some post-op bleeding and a small clot has formed inside the scrotum. Swelling of the scrotal and adjacent tissues, either from surgery or post-op licking by the patient, can also add to the appearance.
This is not usually a big deal. Swelling should resolve within a few days. Physical activity and licking should be kept to a minimum, and for the persistent lickers, an e-collar may be necessary to prevent problems such as infection and premature suture removal by the patient.
When It Is Something To Worry About
The incision should not be actively seeping when you pick up your pet up. Most veterinarians schedule a discharge appointment to go over post-op instructions and care of your dog, including a peek at the incision to make sure everything is OK. If you notice bleeding or seeping after you are home, call your veterinarian or the emergency service for advice.
If your dog is continually licking the incision, speak to your vet sooner rather than later about ways to stop licking. Left unattended, dogs will inflame the skin and remove any sutures they can get to.
If the scrotum is very swollen (turgid) and not stabilizing/shrinking, call your veterinarian as soon as possible to rule out an active internal bleeding situation.
Finally, if the scrotal tissue and/or skin around the incision is red, swollen, extra warm to the touch or seeping with discharge, please call your veterinarian to re-examine and make sure an infection isn't present.Note: For dogs that are cryptorchid, where one or both testicles do not descend into the scrotum, they stay in the abdominal cavity, there will also be an incision on the belly, similar to a spay surgery to find and remove the abdominal testicle(s).