Extrapolated from article written by Dr. Bushby and Dr. Griffin
This is a multi-factorial problem with a tendency to occur regardless of the age at which an animal is spayed or neutered.
Studies have proven this false. The growth plates actually close a little later in fixed animals.
Two major studies have been performed and the results are equivocal. A study at Texas A & M showed no increase in hip dysplasia whereas a study at Cornell showed a slight increase.
Spaying appears to have no influence on the incidence of perivulvar dermatitis. It is actually related to a recessed vulva and made worse by obesity.
The incidence is the same regardless of the age of the dog at the time of the spay.
FELINE URINARY OBSTRUCTION
The diameter of the penile urethra does not change following castration.
Three studies have been performed and the results are equivocal. A study at Texas A & M showed no difference whereas a study at Cornell showed a slight increase. A third study actually found that dogs spayed AFTER their first heat cycle were more likely to have incontinence than if spayed BEFORE the onset of puberty.
We take precautions to keep the body temperature and blood glucose concentration normal while at the hospital. This allows for anesthesia with minimal risk.