General information concerning the various considerations for proceeding with ovariohysterectomy or ovariectomy

The Western Connection
Volume 39 | July 2022

Proposed advantages of proceeding with ovarian removal

  • Avoidance of unwanted pregnancy and cycling behavior/signs. Specifically, this can include wandering, inter-dog aggression, mammary gland development, vaginal hypertrophy, vaginal discharge
  • Elimination of pregnancy associated diseases – dystocia, metritis, mastitis, uterine torsion or prolapse
  • Ovarian neoplasia: Luckily this type of cancer is considered rare in dogs. Both benign and aggressive malignant variants occur. If the ovaries are removed, the risk for cancer development in the ovaries is not possible
  • Vaginal/uterine neoplasia: leiomyoma, leiomyosarcoma. This type of cancer is also relatively rare. Additionally, the vast majority of uterine/vaginal cancer is benign. These cancers are considered to be associated with hormone production from the ovaries. Ovarian removal is considered to be very protective. In some cases, ovarian removal may also stimulate regression of leiomyomas.
  • Cystic endometrial hyperplasia - Chronic changes to the uterus under the influence of ovarian hormones which predisposes to additional disease including: Pyometra, mucometra, hydrometra, hematometra, endometrial polyps. NOTE: Pyometra can become a life-threatening condition due to the severe infectious process within the uterus with many systemic consequences. This is a relatively common condition of intact females. The life-time (10-year) risk has previously been researched to be approximately 24-25%. With ovarian removal, the environment suitable for such diseases should not develop.
  • Vaginal prolapse: Ovarian hormones are considered to predispose to this condition.
  • Mammary neoplasia. Unfortunately, up to 53% of mammary masses can be aggressive cancers. These have the potential to spread to lymph nodes (typically in the abdomen) and the lungs. Removing the hormonal source has been historically proven to be protective. Historical research evaluated the risk for developing mammary cancer to be 0.05% if spayed before the first heat, 8% if spayed after the first but before their second, and 26% if spayed after the second heat. Additionally, this study further identified that dogs spayed after two cycles but before 2.5 years of age still experienced a marked sparing effect for cancer development

Proposed disadvantages of proceeding with ovarian removal

  • Anesthetic risks: Overall, anesthesia is very safe in dogs, however, the procedure is not without potential complications. Preoperative baseline blood and urine testing (if not performed within the prior 6-12 months) is ideally performed to ensure that patients are free from underlying subclinical disease.
  • Surgical complications are very rare; however, complications can inevitably occur in in a small minority of patients. Surgery related complications can include hemorrhage, retained surgical sponge (gossypiboma), and damage to adjacent organs (the intestine, kidneys, ureter, and spleen are all in close proximity to the ovaries).
  • Ovarian remnant syndrome is a rare condition whereby hormones continued to be released from ovarian tissue despite a seemingly unremarkable surgery. The most common cause for this is ovarian tissue which persisted in a normal location despite the surgery. Revision surgery is indicated to remove the tissue.
  • Weight gain: Estrogen is considered to act as a satiety factor. By removing the ovaries, estrogen is removed and satiety may not be as strictly controlled. This is postulated to be a significant reason why spayed dogs are commonly overweight. In one study spayed dogs were considered to be twice as likely to be obese compared to intact dogs. Importantly, the consequences of increased body condition can commonly exacerbate arthritis or other orthopedic conditions that may occur later in life. Monitoring of body condition and weight are recommended postoperatively.
  • Urinary incontinence: Overall, an estimated 0.2-0.3% of intact dogs suffer from urinary incontinence while 19-20% of spayed dogs have been diagnosed to have urinary incontinence over their lifetime. Risk factors identified throughout multiple studies include breed, increased body weight, a short urethral length, caudal bladder position (bladder located further back), and older animals. The age at which families choose to proceed with spaying has come under debate as a point of investigation with mixed and conflicting results. Generally, no definitive association with the age at the time of spay has been identified. Some studies suggest that delaying ovariectomy until over one year of age may be advantageous to some large and giant breed dogs.
  • Cancer: Certain types of cancers have been overrepresented in dogs that have been spayed and castrated in some studies. The jury is still out however and an exact cause-and-effect relationship has yet to be defined. Understandably there are many types of cancer and countless factors that need to be considered when studying the effects of ovary removal on cancer development. Developing a clear understanding has been challenging and remains an ongoing point of research. Guidelines concerning specific breeds have become recently available. Compared to intact animals, spayed dogs may have a ~2-4x increased risk for transitional cell carcinoma (urinary system cancer), ~1.3-2.0x increased risk for osteosarcoma (bone cancer), ~5x increased risk for cardiac hemangiosarcoma (rare heart cancer), and ~2.2x increased risk for splenic hemangiosarcoma (spleen vascular cancer).
  • Growth: The potential effects of sex hormone presence or absence on bone growth during the first year of life has been evaluated in several studies. In one study evaluating the effects of de-sexing at 7 weeks, 7 months, or leaving the dogs intact, the following conclusions were reached. The rate of growth was unaffected; however, the length of the growth period was prolonged in the neutered groups (effect more pronounced when neutered early). As a general rule/guide, for small dogs, the timing of spay is unlikely to significant effect growth, while delayed timing (over 11months or in some cases over 23 months) of ovariectomy for large and giant breed dogs may be advantageous

Other considerations

What kind of surgery should be performed? Traditionally, veterinarians were and still may be trained to remove both the uterus and ovaries (ovariohysterectomy). Over time, our understanding and interventions have evolved to where it is now common to only remove the ovaries (ovariectomy). In short ovariectomy is considered to be the procedure of choice. Historical studies have found no long-term advantage to removing the uterus in addition to the ovaries. This is likely because most reproductive diseases are related to the hormones produced by the ovaries. Removing the ovaries without uterus decreases surgical trauma and, in most hands, also results in a shorter procedure with less time under anesthesia. Removal of both the ovaries and uterus may be indicated in older patients, and especially those with uterine pathology.

In veterinary medicine ovariectomy is traditionally removed via a midline incision in the abdomen. With the evolution of surgical technology, we are now able to offer minimally invasive surgical options via key hole incisions. The proposed advantages of minimally invasive surgery are numerous including but not limited to improved visualization, magnification, decreased surgical trauma, improved comfort, and rapid recovery times. We perform this most typically as a "day procedure" with the patients being discharge into home care that day provided that their recovery from anesthesia is unremarkable. Specifically, the complication rate of minimally invasive surgery has been identified to be approximately half that of traditional surgical techniques in one study. The advantages of minimally invasive approaches become realized in larger dogs as well as those in which a prophylactic gastropexy is considered. This additional procedure only adds approximately 10-15 minutes to the anesthetic time and can be completed with the addition of only one extra 5mm port (ie we perform everything laparoscopically, not laparoscopic assisted).

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