Reproductive Diseases of the Spayed Bitch and Neutered Dog

Neutering—spay or castration— successfully prevents pregnancy and unwanted puppies, prostatic hyperplasia, neoplasia of the mammary glands, uterus, ovaries or testicles, and decreases aggression and behavioral issues. However, neutering directly or indirectly causes other diseases including incontinence, obesity and diabetes, muscle atrophy and hip dysplasia, prostate and bone cancer and dermatitis. This discussion will focus on disease conditions directly related to the reproductive system.

Ovarian Remnants often present as an owner complaint of cyclic abnormalities in behavior, vaginal discharge, vulvar swelling, attraction of male dogs, breeding behavior, or other complaints. An accurate history of the cyclic nature of the condition is necessary to ascertain a reproductive component. Often, clinical signs of ovarian remnants go unnoticed as bloody vaginal discharge will be significantly decreased in the absence of the uterus, and vulvar swelling may be obscure. Incidental findings of remnant ovarian tissue may be subsequent to pathologic changes such as pyometra or ovarian neoplasia.

Vaginal cytology consistent with estrus or a negative luteinizing hormone (LH) test should confirm the presence of ovarian tissue. Normally, ovarian negative feedback suppresses LH release from the anterior pituitary (except during the LH surge of estrus). In ovariectomized animals, LH release is not suppressed and can be measured in sufficiently high concentrations in serum. Therefore, a positive LH test indicates either ovariectomy or a physiologic surge of LH during estrus. A vaginal cytology at the time of LH testing will differentiate the positive test.  [...]