Non-cancerous conditions associated with spay/neuter status in the canine.
Gonadecotmy (GX) represents the most common set of surgeries performed in small animal veterinary medicine in the USA. The most common surgeries in bitches are ovariohysterectomy (OHE) or ovariectomy (OX) via ventral midline approach, or via laparoscopy. The most common surgery in dogs is castration (CX) via either prescrotal or scrotal approach. These are the procedures with which students are routinely taught surgery skills and are considered extremely safe in the USA. However, in the past two decades, there has been increasing awareness of the potential ramifications of these surgeries on individual animals and much discussion both within and outside the veterinary community has focused on the potential risks associated with gonadectomy or leaving an animal intact. The primary societal pressure to perform GX surgeries in the USA is the continuing overpopulation of unwanted dogs and cats and the perception that routine GX will reduce this population. Researchers found that intact animals were at greater risk for relinquishment and unwanted offspring from owned and feral animals represent a major factor contributing to the population of shelter-animals. Supporting the efficacy of spay-neuter programs that were established in the late 1970s and 1980's, several studies have documented declining trends in shelter intake and animals euthanized during the past two decades, mirrored by increasing prevalence of neutered animals in private households in the USA. Recent studies suggest that 64-75% of dogs in the USA are neutered. In addition, GX is frequently performed to promote individual animal health. Several studies examining longevity and health in dogs found that neutered animals live longer and are less likely to suffer from serious reproductive diseases, such as pyometra and non-cancerous prostatic disease, mammary and reproductive tumors of females, roaming and associated traumatic events, disorders related to pregnancy or parturition and unwanted hormone-associated behavior. In contrast, numerous recent publications have identified specific complications associated with GX in individual animals and the effectiveness of spay/neuter programs for population control has been difficult to document, with conflicting results among studies. Because of the conflicting and confusing data available, there is an urgent need for veterinarians to have a nuanced approach to recommendations and to be prepared to discuss the benefits and risks of surgical GX with owners, public interest groups and policy makers. We herein make an effort to succinctly summarize the most important data regarding non-neoplastic health conditions affected by neuter-status. Neoplastic conditions will be addressed in a separate review in this journal and are not the focus of this paper. Major non-neoplastic conditions that have been linked with neuter-status include the following: pyometra, surgical complications, ovarian remnant syndrome, behavioral problems/anxiety, prostatic disease, urinary incontinence, cystitis, obesity, hip dysplasia and cruciate ligament rupture. In addition, numerous other conditions have been reported anecdotally, but are not as well supported in the literature. Estimated incidence, effect of neuter and breed predispositions of selected conditions described in the literature have been summarized in the Table.