Howe, DVM: rebuttal to k9-Athlete/Zink, DVM - Pt II
here is the rest of the article, With the Refs -
Quote:
Other Health Considerations
Dr. Zink mentions other health considerations that should be considered when deciding whether the canine athlete should undergo gonadectomy at, or before, 6 months of age. Dr. Zink states: “A number of studies have shown that there is an increase in the incidence of female urinary incontinence in dogs spayed early”, and gives one reference for this (Stocklin-Gautschi, 2001). Indeed, there have been several studies that have demonstrated an increased incidence of urinary incontinence in dogs spayed early, as well as a study that demonstrated a much higher incidence of urinary incontinence (20.1%) in bitches spayed after the first estrus, as compared to those spayed before the first estrus (Arnold, 1992). In fact, in the reference (Stocklin-Gautschi, 2001) that Dr. Zink quotes, the authors go on to interpret the findings of their study in relation to similarly performed studies, and then state in the discussion: “A comparison of the present results with those of Arnold, et al. (1992) indicates that the risk of urinary incontinence is lower in early spayed bitches than in bitches spayed after the first oestrus, but that the clinical signs of the affected animals are significantly more pronounced.” The authors continue and state: “However, assuming that most incontinent bitches respond well to medication, this factor is of minor importance. This relative disadvantage of early spaying is negligible when compared with the benefits, such as lower incidence of urinary incontinence and the protection against mammary tumours.” On the other hand, the recent study of 1842 dogs by Spain, et al., demonstrated that there was an increased incidence of urinary incontince in female dogs, with the risk being greatest in females gonadectomized before 3 months of age, compared with those gonadectomized at, or after, 3 months of age (Spain, 2004). Based upon their findings, Spain concludes: “Because urinary incontinence was greater among puppies gonadectomized before 3 months of age and incontinence can be a lifelong condition requiring ongoing treatment, it is reasonable to conclude that female dogs should not be gonadectomized until at least 3 to 4 months of age.” The authors continue: “This may be particularly prudent for a shelter that does not have an excess of puppies and is focused on reducing medical and behavioral conditions that could lead to relinquishment of adolescent and adult dogs. Conversely, for shelters with excess puppies, the advantages of gonadectomy of all dogs before adoption may outweigh the risk of urinary incontinence.”
Dr. Zink also points out that neutering of male dogs has been associated with an increased likelihood of urethral sphincter incontinence (Aaron, 1996) and seems to imply that early neutering plays a role in this. However, when one examines Aaron’s paper, it becomes obvious that the dogs that developed urethral sphincter incompetency following castration were adult dogs when castrated, with the median age of onset of urinary incontinence being 6 years (range 6 months to 10.5 years), and the median period between castration and the onset of incontinence being 10 days (range “immediately” to 18 months). Clearly, this paper should not be quoted as an argument against early neutering (or late neutering, for that matter) in male dogs. Urethral sphincter incompetency is quite uncommon in male dogs, and is likely multifactorial in nature, considering male dogs don’t tend to respond well to hormonal replacement (Aaron, 1996). When one considers the incidence of prostatic hyperplasia, cysts, and abscesses in older male dogs (much higher than urethral sphincter incompentency), and the potential life threatening nature of some of these problems, the role for castration in preventative health care for male dogs becomes obvious.
Hypothyroidism is cited as another health reason to avoid early gonadectomy. Dr. Zink is correct that both the cited references (http://www.grca.org/healthsurvey.pdf and Panciera, 1994) do demonstrate that hypothyroidism occurs more commonly in gonadectomized dogs (including the Golden Retriever breed) than in intact dogs. While there is an association, the overall incidence of hypothyroidism is 0.2% in canines (Panciera, 1994 - although it may be higher in certain breeds such as the Golden Retriever and Doberman Pinscher). It would not be prudent to discourage spaying/castrating of dogs (early or not) to prevent a disease with such a low incidence that has a good response to treatment in most dogs (Panciera, 1994), when other diseases have much higher incidences (mammary neoplasia, pyometra, prostatic hyperplasia, etc.) and may not have as favorable an outcome.
Infectious diseases are cited as another reason to avoid early gonadectomy. While Dr. Zink does correctly state the findings of the cited reference which were that infectious diseases were more common in dogs spayed/castrated at 24 weeks of age or less as compared to those undergoing gonadectomy at more than 24 weeks (Howe, 2001), Dr. Zink fails to point out the conclusions of the author related to this issue. Howe notes in that article that: “Parvoviral enteritis was the most commonly reported infectious disease and was reported exclusively in dogs that underwent prepubertal gonadectomy. Parvovirus enteritis is common from puppies from shelter environments, but uncommon in older dogs. The potential influence of anesthesia and surgery on the incidence of parvoviral enteritis in puppies that underwent gonadectomy could not be determined in our study, because comparisons with puppies that did not undergo gonadectomy were not performed.” Spain’s study of 1842 dogs also found that dogs gonadectomized before 5.5 months had a significantly greater incidence of parvoviral enteritis (as compared to those gonadectomized later), but went on to say: “In that study (Howe, 2001), as with ours, however, the increased rate of parvovirus infection probably represented increased susceptibility of dogs < 6 months of age during the periadoption period and not long-term immune suppression or long-term susceptibility as a result of early-age gonadectomy” (Spain, 2004).
Interestingly, Dr. Zink did not address one of the major health concerns of the unspayed bitch which is pyometra, a potentially life threatening condition. Pyometra occurs at a very high rate in unspayed bitches, and the incidence has been reported to approach 66% in bitches over 9 years of age (Johnston, 2001). Unlike the United States, in Scandinavian countries, female dogs are at risk of developing pyometra since elective neutering of healthy bitches is seldom performed, resulting in only 7% of bitches being spayed (Egenvall, 1999). A recent study in Sweden was conducted to assess the incidence of pyometra in bitches using data obtained from a Swedish pet insurance company, and it was found that overall, almost 25% of the insured dog population had developed pyometra by 10 years of age. In the three breeds at highest risk of developing the disease (rough-haired Collie, Rottweiler, Bernese Mountain Dog), approximately 50% of the bitches had experienced pyometra before reaching 10 years of age (Hagman, 2004). Pyometra can be a life threatening, and expensive to treat, condition that occurs with much greater frequency than rupture of the cranial cruciate ligament or cardiac tumors, and can easily be prevented by ovariohysterectomy.
In summary, while I respectfully disagree with Dr. Zink as to the most appropriate time at which to gonadectomize the animal that is not used for breeding purposes, it is important for any veterinarian to base their decisions upon a well versed understanding of the scientific literature. As new studies are performed, and our knowledge base grows as to the effects, both good and bad, of sterilization of pet animals (including “early age” gonadectomy), current recommendations may (or may not) be changed. With regard to the canine athlete, I would encourage those who feel that they are seeing certain problems more frequently in animals that have undergone early age gonadectomy (as compared to traditional age gonadectomy) to collect, and analyze, data and contribute the information to the scientific literature. Until such studies are performed, anecdotal information remains just that – anecdotal, unverified, and unsuitable for making broad sweeping recommendations regarding the appropriateness of spaying and castrating (at any age) animals that are not used for breeding purposes (or for making recommendations regarding tubal ligation/vasectomy which clearly don’t have the same health benefits as gonadectomy).
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30-07-2010, 02:08 AM
how long has this procedure been performed? [just how safe is this?]
NOT ped-S/N but a classic example of coincidence vs causes
Linear Mode
