Both tubal ligation (TL) and ovary sparing spay (OSS) are procedures which may be utilized in veterinary medicine to achieve sterilization of the female patient. Research shows both procedures to be superior to traditional spay (i.e., ovariohysterectomy) with respect to the disposition of sex hormones – essential components of a healthy metabolism, immune system and brain function, as well as the physical and mental development of our canine friends. Furthermore, in part because of its minimally invasive nature, we believe tubal ligation to be the superior sterilization technique.
With a tubal ligation, the fallopian tubes are cut and tied off, and no organs are removed. By retaining the ovaries and uterus, the sex hormones remain undisturbed. There are veterinary practitioners who advocate for OSS, which is essentially the equivalent of a human hysterectomy – the ovaries are retained and only the uterus is removed. The OSS is termed a “hormone-sparing” procedure as endocrinology textbooks have historically described the non-pregnant uterus as ‘dormant,’ ‘quiescent,’ and ‘useless.’
One of the purported advantages of OSS is that by removing the uterus, you are eliminating the risk of pyometra. However, it is not uncommon for surgeons to inadvertently leave some portion of the uterus behind. The remaining uterine tissue is very susceptible to pyometra, so much so, that there is a term for this phenomenon, i.e., “stump pyometra”.
Another benefit claimed by vets recommending OSS, is that this procedure requires no additional training for vets, as it is a subset of the traditional spay.
In 2017, research scientists in Italy hypothesized hormones produced by female dogs’ ovaries affected not only reproduction, but were also instrumental in the proper cognitive functioning of female dogs’ brains. Accordingly, their statement of the problem was:
“In spite of the frequency with which dogs’ gonadectomy [(i.e., spay/ovariohysterectomy)] is advised in most western countries, its consequences on cognitive abilities remain virtually unknown…”.184
In order to prove/disprove their hypothesis, they devised a study to evaluate the effect of ovariectomy (i.e., removal of the ovaries only) on specific female dogs’ cognitive functions. Spatial learning, memory and reversal learning skills were assessed in 64 pet dogs. The findings of the study were:
- Speed of learning and accuracy was highest in intact females.
- Success rate in the learning and memory task was highest in intact females.
These results were the first evidence of a non-reproductive effect (i.e. an effect on brain function) of ovariectomy specifically in dogs.184
A 2012 study in Neurodegenerative Diseases explored the association of hysterectomy and oophorectomy (i.e., ovary removal) with the subsequent risk of cognitive impairment or dementia in women. The study concluded:
“Compared with women with no gynecologic surgeries, the risk of cognitive impairment or dementia was increased in women who had hysterectomy alone, further increased in women who had hysterectomy with unilateral oophorectomy, and further increased in women who had hysterectomy with bilateral oophorectomy. The risk increased with younger age at the time of the surgery. …Estrogen deficiency appears to play a key role in these associations, and estrogen therapy may partly offset the negative effects of the surgeries.”191
An Arizona State research group wanted to compare cognitive function among rats to assess effects of surgical variations, and in particular the influence of the uterus. The participating professor of psychology, Heather Bimonte-Nelson, explained:
“In the past few decades, there has been a significant amount of research on hormones coming primarily from the ovaries, such as estrogens and progesterone, including how they influence brain and body systems outside of reproduction, such as cognition. …In fact, most research has focused on the ovary-brain connection, and little research has been dedicated to understanding the role of the uterus outside of reproduction. Evolutionarily, it does not make sense that a single organ or body system has just one sole function.”
The Arizona State study utilized 4 groups of rats distinguished by their surgical status:
- rats that had no surgery (intact)
- hysterectomy (OSS)
- ovariohysterectomy (spay)
The spacial, working, and reference memory of the groups of rats were compared, and uterus removal alone had a unique detrimental impact on the ability to handle a high-demand working memory load. Results indicate that there is an ovarian-uterus-brain system that becomes interrupted when the reproductive tract has been disrupted, leading to alterations in brain functioning and most probably accelerated brain aging. The study concludes:
“…we report that the nonpregnant uterus itself is not a quiescent organ. Rather, uterus removal with or without concomitant ovarian removal can have significant effects on physiology and cognition, opening new doors for future investigations into the role of the uterus in behavioral outcomes across the lifespan.”177
Consequently, we recommend tubal ligation over OSS as the superior sterilization procedure for the health and happiness of your best friend.