狗狗绝育的好处和坏处

2014-09-22 10:50阅读：9,333

以下论文来自维基百科，翻译：蓝炯。

Long-Term Health Risks and Benefits Associated with Spay / Neuter in Dogs
母犬卵巢摘除手术和公犬阉割手术[译者按: 以下统称绝育手术]的长期健康风险及益处
Laura J. Sanborn, M.S./劳拉 J. 桑伯恩，外科硕士
May 14, 2007/2007年5月14日
Precis 摘要 (略)
INTRODUCTION 引言
Dog owners in America are frequently advised to spay/neuter their dogs for health reasons. A number of health benefits are cited, yet evidence is usually not cited to support the alleged health benefits.
在美国，宠物犬主常常会收到让他们的狗狗做绝育的建议，理由是为了狗狗的健康。虽然在建议绝育时会列出一大堆绝育对健康的好处，但通常却并不会同时列出证据来支持所宣称的好处。
When discussing the health impacts of spay/neuter, health risks are often not mentioned. At times, some risks are mentioned, but the most severe risks usually are not.
当人们在讨论绝育对健康的影响时，对于绝育会带来的健康风险却往往闭口不谈。虽然偶尔也会提到一些风险，但绝大多数严重的风险却通常不会提及。
This article is an attempt to summarize the long-term health risks and benefits associ

ated with spay/neuter in dogs that can be found in the veterinary medical literature. This article will not discuss the impact of spay/neuter on population control, or the impact of spay/neuter on behavior.
本文尝试对于在兽医医学文献中可以找到的，和母犬/公犬绝育相关的长期健康风险和益处进行总结。对绝育会对犬只数量控制或者犬的行为方面的影响本文不做讨论。
Nearly all of the health risks and benefits summarized in this article are findings from retrospective epidemiological research studies of dogs, which examine potential associations by looking backwards in time. A few are from prospective research studies, which examine potential associations by looking forward in time.
本文所总结的几乎所有健康风险和益处均为犬的流行病学回溯性研究发现。这些研究通过回顾过去来考察潜在的关联关系。还有少量的为前瞻性研究，通过展望将来考察潜在的关联关系。
SUMMARY 概要
An objective reading of the veterinary medical literature reveals a complex situation with respect to the long term health risks and benefits associated with spay/neuter in dogs. The evidence shows that spay/neuter correlates with both positive AND adverse health effects in dogs. It also suggests how much we really do not yet understand about this subject.
对兽医医学文献客观的阅读揭示了和母犬/公犬绝育手术相关的长期健康风险和益处。证据显示绝育既会给犬带来正面的健康影响，同时也会带来负面的健康影响。它同时也让我们意识到我们在这个问题上认识的匮乏。
On balance, it appears that no compelling case can be made for neutering most male dogs, especially immature male dogs, in order to prevent future health problems. The number of health problems associated with neutering may exceed the associated health benefits in most cases.
总之，似乎无法举出令人信服的案例可以说明对大多数公犬，尤其是发育未成熟的公犬，进行绝育是为了预防将来的健康问题。在大多数案例中，公犬绝育所引起的健康问题可能要超过所带来的健康益处。
On the positive side, neutering male dogs
公犬绝育手术的正面影响：
• eliminates the small risk (probably <1%) of dying from testicular cancer
消除死于睾丸癌的微弱风险(可能性<1%)
• reduces the risk of non-cancerous prostate disorders
降低患非癌性前列腺疾病的风险
• reduces the risk of perianal fistulas
降低患肛周瘘管的风险
• may possibly reduce the risk of diabetes (data inconclusive)
可能可以降低患糖尿病的风险(数据不具结论性)
On the negative side, neutering male dogs
公犬绝育手术的负面影响：
• if done before 1 year of age, significantly increases the risk of osteosarcoma (bone cancer); this is a common cancer in medium/large and larger breeds with a poor prognosis.
如果在1周岁之前手术,会显著增加患骨肉瘤(即骨癌)的风险。骨肉瘤是在中型和大型犬中的一种常见癌症，预后很差。
• increases the risk of cardiac hemangiosarcoma by a factor of 1.6
患心脏血管瘤的风险会增加1.6倍。
• triples the risk of hypothyroidism
患甲状腺功能减退的风险增加到3倍。
• increases the risk of progressive geriatric cognitive impairment
增加患老年认知障碍的风险。
• triples the risk of obesity, a common health problem in dogs with many associated health problems
患肥胖症的风险增加到3倍。肥胖是犬的常见健康问题，会引发很多其它健康问题。
• quadruples the small risk (<0.6%) of prostate cancer
患前列腺癌的风险增加到4倍（犬患前列腺癌的几率很小，为<0.6%）。
• doubles the small risk (<1%) of urinary tract cancers
患尿路癌的风险增加到2倍（犬患尿路癌的几率也很小，为<1%）
• increases the risk of orthopedic disorders
增加患骨科疾病的风险。
• increases the risk of adverse reactions to vaccinations
增加发生免疫不良反应的风险。
For female dogs, the situation is more complex. The number of health benefits associated with spaying may exceed the associated health problems in some (not all) cases. On balance, whether spaying improves the odds of overall good health or degrades them probably depends on the age of the female dog and the relative risk of various diseases in the different breeds. 对于母犬，情况则要复杂得多。由绝育手术所带来的健康方面的好处对于某些犬（不是所有犬）来说，可能要超过所带来的健康问题。总的来说，绝育是会提高还是降低总体健康的几率可能要取决于母犬的年龄，以及各种疾病对于不同犬种的相对风险的大小。
On the positive side, spaying female dogs
母犬绝育手术的正面影响：
• if done before 2.5 years of age, greatly reduces the risk of mammary tumors, the most common malignant tumors in female dogs
如果在2.5周岁前实施手术会极大地降低患乳腺肿瘤的风险。乳腺肿瘤是母犬中最常见的恶性肿瘤。
• nearly eliminates the risk of pyometra, which otherwise would affect about 23% of intact female dogs; pyometra kills about 1% of intact female dogs
几乎可以消除患子宫蓄脓的风险。而未实施绝育手术的母犬患子宫蓄脓的几率大约为23%。有大约1%的未绝育母犬因患子宫蓄脓而死亡。
• reduces the risk of perianal fistulas
降低患肛周瘘管的风险。
• removes the very small risk (_0.5%) from uterine, cervical, and ovarian tumors
消除患子宫肿瘤，宫颈肿瘤以及卵巢肿瘤的风险（母犬患这类疾病的几率本身就很低，为0.5%）
On the negative side, spaying female dogs
母犬绝育手术的负面影响:
• if done before 1 year of age, significantly increases the risk of osteosarcoma (bone cancer); this is a common cancer in larger breeds with a poor prognosis
如果在1周岁前实施手术，会极大地增加患骨肉瘤（即骨癌）的风险。骨癌是较大型犬种中的常见癌，预后很差。
• increases the risk of splenic hemangiosarcoma by a factor of 2.2 and cardiac hemangiosarcoma by a factor of >5; this is a common cancer and major cause of death in some breeds
患脾脏血管瘤的风险增加到2.2倍，患心脏血管瘤的风险增加到>5倍。血管瘤是犬的常见癌症，是某些品种犬的主要死因。
• triples the risk of hypothyroidism
患甲状腺功能减退的风险增加到3倍。
• increases the risk of obesity by a factor of 1.6-2, a common health problem in dogs with many associated health problems
患肥胖症的风险增加到1.6-2倍。肥胖是犬的常见健康问题，会引发很多其它健康问题。
• causes urinary “spay incontinence” in 4-20% of female dogs
引起4-20%的母犬患“绝育尿失禁”症。
• increases the risk of persistent or recurring urinary tract infections by a factor of 3-4
患持续尿路感染或重复发生尿路感染的风险增加到3-4倍。
• increases the risk of recessed vulva, vaginal dermatitis, and vaginitis, especially for female dogs spayed before puberty
增加外阴凹陷，阴道性皮炎以及阴道炎的风险，尤其是对于在青春期之前做绝育手术的母犬。
• doubles the small risk (<1%) of urinary tract tumors
患尿路肿瘤的微小风险（<1%）增加至2倍。
• increases the risk of orthopedic disorders
增加患骨骼系统疾病的风险。
• increases the risk of adverse reactions to vaccinations
增加发生免疫不良反应的风险。
One thing is clear – much of the spay/neuter information that is available to the public is unbalanced and contains claims that are exaggerated or unsupported by evidence. Rather than helping to educate pet owners, much of it has contributed to common misunderstandings about the health risks and benefits associated of spay/neuter in dogs.
有一点非常清楚-公众所获得的关于犬绝育的信息是不完全的，包含了许多夸大其词或者没有事实依据的论断。与其说这些信息起到了教育宠物主人的作用，不如说有许多信息导致了一些常见错误观念，使人们错误地认识和绝育手术相关的健康风险和益处。
The traditional spay/neuter age of six months as well as the modern practice of pediatric spay/neuter appear to predispose dogs to health risks that could otherwise be avoided by waiting until the dog is physically mature, or perhaps in the case of many male dogs, foregoing it altogether unless medically necessary.
传统的绝育时机（6个月）以及现代在幼儿时期就进行绝育的做法有可能使犬更容易罹患疾病，而这些疾病原本是可以避免的，如果1）等犬生理成熟之后再绝育；或者2）对于众多的公犬来说，干脆不做绝育，等到医疗必要时再做。
The balance of long-term health risks and benefits of spay/neuter will vary from one dog to the next. Breed, age, and gender are variables that must be taken into consideration in conjunction with non-medical factors for each individual dog. Across-the-board recommendations for all pet dogs do not appear to be supportable from findings in the veterinary medical literature.
绝育所带来的长期的健康风险和益处视不同的个体而不同。犬种，年龄以及性别都是可变因素，需作为每一只狗的非医学因素考虑在内。兽医医学文献的研究结果不支持一刀切地对所有宠物犬做出关于绝育方面的建议。
FINDINGS FROM STUDIES
研究发现
This section summarizes the diseases or conditions that have been studied with respect to spay/neuter in dogs.
本章节总结了针对绝育犬只进行的疾病或症状的研究。

Complications from Spay/Neuter Surgery
绝育手术并发症
All surgery incurs some risk of complications, including adverse reactions to anesthesia, hemorrhage, inflammation, infection, etc. Complications include only immediate and near term impacts that are clearly linked to the surgery, not to longer term impacts that can only be assessed by research studies.
任何手术都会有一定的风险，包括对麻药的不良反应，出血，发炎，感染等。并发症仅包括明确由手术引起的直接的和近期的影响，而不包括那些只能通过研究才能确定的长期的影响。
At one veterinary teaching hospital where complications were tracked, the rates of intraoperative, postoperative and total complications were 6.3%, 14.1% and 20.6%, respectively as a result of spaying female dogs1. Other studies found a rate of total complications from spaying of 17.7%2 and 23%3. A study of Canadian veterinary private practitioners found complication rates of 22% and 19% for spaying female dogs and neutering male dogs, respectively4.
有一家兽医教学医院通过对并发症的跟踪发现，接受绝育手术的母犬在术中，术后以及总体并发症的发生率分别为6.3%，14.1%和20.6%。其它一些研究发现母犬绝育手术并发症总体发生率为17.7%和23%。一项关于加拿大私立兽医诊所的调查发现绝育母犬和公犬的并发症发生率分别为22%和19%。
Serious complications such as infections, abscesses, rupture of the surgical wound, and chewed out sutures were reported at a 1- 4% frequency, with spay and castration surgeries accounting for 90% and 10% of these complications, respectively.4
The death rate due to complications from spay/neuter is low, at around 0.1%2.
严重并发症，例如感染，脓肿，手术伤口破裂，以及缝线咬出的发生率据报告为1-4%,其中母犬绝育手术和公犬绝育手术发生这些并发症的分别占90%和10%。
在犬的绝育手术中因并发症而死亡的比例很低，大约为0.1%。

Prostate Cancer 前列腺癌
Much of the spay/neuter information available to the public asserts that neutering will reduce or eliminate the risk that male dogs develop prostate cancer. This would not be an unreasonable assumption, given that prostate cancer in humans is linked to testosterone. But the evidence in dogs does not support this claim.
公众可以获得的许多关于母犬/公犬绝育的信息宣称绝育可以降低或者消除公犬患前列腺癌的风险。鉴于人类的前列腺癌的确和睾丸素相关，因此这可能并非是一个不合理的假设。但我们从犬类身上所获得的证据却并不支持这个观点。
In fact, the strongest evidence suggests just the opposite.
事实上，最有力的证据却恰恰支持相反的观点。
There have been several conflicting epidemiological studies over the years that found either an increased risk or a decreased risk of prostate cancer in neutered dogs. These studies did not utilize control populations, rendering these results at best difficult to interpret. This may partially explain the conflicting results.
近年来，有一些相互冲突的流行病学研究发现，在绝育公犬中前列腺癌的发生有上升或者下降的几率。这些研究没有利用对照犬群，因此研究结果显得非常难以解释。这可能就是出现矛盾结果的部分原因。
More recently, two retrospective studies were conducted that did utilize control populations. One of these studies involved a dog population in Europe5 and the other involved a dog population in America6. Both studies found that neutered male dogs have a four times higher risk of prostate cancer than intact dogs.
更近的一些时候，有人利用对照犬群进行了两项回溯性的研究。其中一项研究涵盖了欧洲的一些犬群，而另一项研究则涵盖了美国的一些犬群。两项研究均发现绝育公犬患前列腺癌的机率要比未绝育公犬高4倍。
Based on their results, the researchers suggest a cause-and-effect relationship: “this suggests that castration does not initiate the development of prostatic carcinoma in the dog, but does favor tumor progression”5 and also “Our study found that most canine prostate cancers are of ductal/urothelial origin….The relatively low incidence of prostate cancer in intact dogs may suggest that testicular hormones are in fact protective against ductal/urothelial prostatic carcinoma, or may have indirect effects on cancer development by changing the environment in the prostate.”6
根据研究结果，研究者认为其中的因果关系是这样的：“这说明去势手术虽然不会引发犬的前列腺癌，但确实会有利于肿瘤的生长”，以及“我们的研究发现绝大多数犬类前列腺癌为导管或者膀胱上皮原发性。。。。。。而未绝育公犬前列腺癌的低发率可能也提示我们事实上睾丸激素对于防止导管性前列腺癌/膀胱上皮性前列腺癌的发生是起到保护作用的。或者有可能因为改变了前列腺内的环境而对前列腺癌的生长有着间接的影响。”
This needs to be put in perspective. Unlike the situation in humans, prostate cancer is uncommon in dogs.
不过我们也需要客观地看待这个结论。和人类的情况不同，前列腺癌在犬类中很少发生。
Given an incidence of prostate cancer in dogs of less than 0.6% from necropsy studies7, it is difficult to see that the risk of prostate cancer should factor heavily into most neutering decisions. There is evidence for an increased risk of prostate cancer in at least one breed (Bouviers)5, though very little data so far to guide us in regards to other breeds.
根据尸检报告，犬类前列腺癌的发生率为不到0.6%。鉴于此，我们很难将前列腺癌的风险作为决定大多数公犬是否需要绝育的重要决定因素。虽然对于其它犬种目前的数据还很少，但至少在一个犬种（法兰德斯牧犬）中有证据表明前列腺癌的风险会增加。

Testicular Cancer 睾丸癌
Since the testicles are removed with neutering, castration removes any risk of testicular cancer (assuming the castration is done before cancer develops). This needs to be compared to the risk of testicular cancer in intact dogs.
由于在做绝育手术时已摘除睾丸，因此绝育同时也消除了任何患睾丸癌的风险（假设在实施手术前没有发生癌变）。这需要和未做绝育的公犬患睾丸癌的风险相对比。
Testicular tumors are not uncommon in older intact dogs, with a reported incidence of 7%8. However, the prognosis for treating testicular tumors is very good owing to a low rate of metastasis9, so testicular cancer is an uncommon cause of death in intact dogs. For example, in a Purdue University breed health survey of Golden Retrievers10, deaths due to testicular cancer were sufficiently infrequent that they did not appear on list of significant causes of 'Years of Potential Life Lost for Veterinary Confirmed Cause of Death” even though 40% of GR males were intact. Furthermore, the GRs who were treated for testicular tumors had a
90.9% cure rate. This agrees well with other work that found 6-14% rates of metastasis for testicular tumors in dogs11.
未绝育老年公犬患睾丸癌并不少见，报告发生率为7%。但是，由于转移率很低，睾丸癌的治疗预后非常好，因此死于睾丸癌的未绝育公犬相当少。例如，美国普渡大学（Purdue University，一所历史悠久的研究性大学）所开展的一项关于金毛猎犬的调查显示，死于睾丸癌的病例非常少，因此睾丸癌没有被列入“兽医确认的死亡原因所造成的潜在损失寿命年限”表中的重要死亡原因，尽管有40%的雄性金毛猎犬没有做过绝育手术。此外，接受过睾丸癌治疗的金毛猎犬的治愈率为90.9%。这个结果和另外一项研究的发现相吻合。该项研究发现犬类睾丸癌的转移率为6-14%。
The high cure rate of testicular tumors combined with their frequency suggests that fewer than 1% of intact male dogs will die of testicular cancer.
睾丸癌的高治愈率及其发生率综合起来提示未绝育公犬死于睾丸癌的比例小于1%。
In summary, though it may be the most common reason why many advocate neutering young male dogs, the risk from life threatening testicular cancer is sufficiently low that neutering most male dogs to prevent it is difficult to justify.
总之，尽管这是许多人提倡在公犬幼年时就进行绝育的最常见理由，但睾丸癌威胁生命的风险却是相当低，因此以预防睾丸癌为理由对大多数公犬实施绝育手术难以立足。
An exception might be bilateral or unilateral cryptorchids, as testicles that are retained in the abdomen are13.6 times more likely to develop tumors than descended testicles12 and it is also more difficult to detect tumors in undescended testicles by routine physical examination.
双侧或单侧隐睾的公犬则是一个例外情况。因为滞留在腹腔的睾丸发生肿瘤的可能性比正常下降睾丸要高13.6倍，而且在常规体检中也更难检查出肿瘤。

Osteosarcoma (Bone Cancer) 骨肉瘤（骨癌）
A multi-breed case-control study of the risk factors for osteosarcoma found that spay/neutered dogs (males or females) had twice the risk of developing osteosarcoma as did intact dogs13.
一项在多品种犬群中开展的，针对骨肉瘤风险因素所进行的病例对照研究发现，绝育母犬/公犬发生骨肉瘤的几率是未绝育犬的2倍。
This risk was further studied in Rottweilers, a breed with a relatively high risk of osteosarcoma. This retrospective cohort study broke the risk down by age at spay/neuter, and found that the elevated risk of osteosarcoma is associated with spay/neuter of young dogs14. Rottweilers spayed/neutered before one year of age were 3.8 (males) or 3.1 (females) times more likely to develop osteosarcoma than intact dogs.
研究者还针对患骨肉瘤风险相对较高的罗威纳犬开展了调查。这项回溯性定群研究将风险按绝育年龄进行分类，结果发现幼犬绝育和患骨肉瘤几率骤升相关。在1周岁前绝育的罗威纳犬患骨肉瘤的几率比未绝育犬要高3.8倍（公犬）或者3.1倍（母犬）。
Indeed, the combination of breed risk and early spay/neuter meant that Rottweilers spayed/neutered before one year of age had a 28.4% (males) and 25.1% (females) risk of developing osteosarcoma. These results are consistent with the earlier multi-breed study13 but have an advantage of assessing risk as a function of age at neuter. A logical conclusion derived from combining the findings of these two studies is that spay/neuter of dogs before 1 year of age is associated with a significantly increased risk of osteosarcoma.
事实上，综合考虑犬种及早期绝育因素意味着在1周岁前绝育的罗威纳犬患骨肉瘤的几率分别为28.4%（公犬）和25.1%（母犬）。这些结果和前面所提到的多犬种研究是一致的，但优点是可以根据绝育年龄对患骨肉瘤的风险进行评估。从这两项研究中可以得出的一个符合逻辑的结论是：在1周岁之前绝育的公犬和母犬患骨肉瘤的风险会大大提高。
The researchers suggest a cause-and-effect relationship, as sex hormones are known to influence the maintenance of skeletal structure and mass, and also because their findings showed an inverse relationship between time of exposure to sex hormones and risk of osteosarcoma.14
研究者认为在绝育和骨肉瘤之间存在因果关系，因为性激素会对维护骨骼的结构和内容产生影响，而且他们的发现也显示了暴露在性激素下的时间长短和患骨肉瘤的几率成反比。

The risk of osteosarcoma increases with increasing breed size and especially height13. It is a common cause of death in medium/large, large, and giant breeds. Osteosarcoma is the third most common cause of death in Golden Retrievers10 and is even more common in larger breeds13.
患骨肉瘤的风险随犬种的增大，尤其是犬身高的增加而增加。骨肉瘤是中大型以及巨型犬种的常见死因。在金毛猎犬的常见死因中,骨肉瘤位居第三。而在更大型犬种的常见死因中，骨肉瘤的排名甚至还要靠前。
Given the poor prognosis of osteosarcoma and its frequency in many breeds, spay/neuter of immature dogs in the medium/large, large, and giant breeds is apparently associated with a significant and elevated risk of death due to osteosarcoma.
鉴于骨肉瘤的预后很差及其在许多犬种中的多发性，对中大型，大型以及巨型犬的未成熟犬进行绝育会明显导致因骨肉瘤而死亡的风险骤增。

Mammary Cancer (Breast Cancer) 乳腺肿瘤（乳房癌）
Mammary tumors are by far the most common tumors in intact female dogs, constituting some 53% of all malignant tumors in female dogs in a study of dogs in Norway15 where spaying is much less common than in the USA.
乳腺肿瘤是迄今为止在未绝育母犬中最常见的肿瘤。在挪威进行的一项犬类研究发现，乳腺癌占母犬所有恶性肿瘤的53%。而在挪威母犬做绝育的比例要远远低于美国。
50-60% of mammary tumors are malignant, for which there is a significant risk of metastasis16. Mammary tumors in dogs have been found to have estrogen receptors17, and the published research18 shows that the relative risk (odds ratio) that a female will develop mammary cancer compared to the risk in intact females is dependent on how many estrus cycles she experiences:
50-60%的乳腺肿瘤为恶性肿瘤，因为其发生转移的几率非常高。研究发现，犬的乳腺肿瘤中具有雌激素受体，而一项公开的研究显示和未绝育母犬的风险相比，母犬发生乳腺癌的相对风险（比值比）取决于母犬的发情次数：
# of estrus cycles before spay/绝育前发情次数 Odds Ratio/比值比
None/从未发情 0.005
1 0.08
2 or more/2次或以上 0.26
Intact/未绝育 1.00
The same data when categorized differently showed that the relative risk (odds ratio) that females will develop mammary cancer compared to the risk in intact females indicated that:
同样的数据以不同方式归类后显示和未绝育母犬的风险相比，母犬发生乳腺癌的相对风险（比值比）为：
Age at Spaying/绝育时犬龄 Odds Ratio/比值比
_ 29 months/29个月 0.06
_ 30 months/30个月 0.40 (not statistically significant at the P<0.05 level)
Intact/未绝育 1.00
Please note that these are RELATIVE risks. This study has been referenced elsewhere many times but the results have often been misrepresented as absolute risks.
请注意，上述数据为相对风险。该项研究曾被多次在别处引用，但研究结果却常常被错误地表示为绝对风险。
A similar reduction in breast cancer risk was found for women under the age of 40 who lost their estrogen production due to “artificial menopause”19 and breast cancer in humans is known to be estrogen activated.
在40岁以下因“人为绝经”而停止分泌雌激素的妇女中也能见到类似的，乳腺癌风险降低的情况。而人类中的乳腺癌已知是由雌激素引发的。
Mammary cancer was found to be the 10th most common cause of years of lost life in Golden Retrievers, even though 86% of female GRs were spayed, at a median age of 3.4 yrs10.
Considering that the female subset accounts for almost all mammary cancer cases, it probably would rank at about the 5th most common cause of years of lost life in female GRs. It would rank higher still if more female GRs had been kept intact up to 30 months of age.
在金毛猎犬中，乳腺癌被列为第10大常见寿命损失原因，尽管有86%的雌性金毛猎犬在平均犬龄为3.4岁时已经绝育。鉴于母犬组占据了几乎所有乳腺癌的病例，因此乳腺癌极有可能是雌性金毛猎犬的第5大常见寿命损失原因。如果有更多的雌性金毛猎犬在30月龄前未进行绝育，那么乳腺癌致死的排名恐怕还要靠前。
Boxers, cocker spaniels, English Springer spaniels, and dachshunds are breeds at high risk of mammary tumors15. A population of mostly intact female Boxers was found to have a 40% chance of developing mammary cancer between the ages of 6-12 years of age15. There are some indications that purebred dogs may be at higher risk than mixed breed dogs, and purebred dogs with high inbreeding coefficients may be at higher risk than those with low inbreeding coefficients20. More investigation is required to determine if these are significant.
拳师犬，可卡犬，英国史宾格犬以及腊肠犬均为乳腺肿瘤的高危犬种。一项针对一群多数为未绝育母犬的拳师犬群体的调查发现，有40%的犬在6-12岁期间罹患了乳腺癌。有一些迹象表明，纯种犬比混种犬患乳腺癌的机率要高，而近亲交配系数高的纯种犬则有可能比近亲交配系数低的纯种犬患乳腺癌的机率要高。如果这项结果意义重大的话，则尚且需要进行更多的调研来下定论。
In summary, spaying female dogs significantly reduces the risk of mammary cancer (a common cancer), and the fewer estrus cycles experienced at least up to 30 months of age, the lower the risk will be.
总之，对母犬进行绝育能大大减小乳腺癌（常发癌症）的风险，而至少在30月龄前，发情次数越少，风险就越小。

Female Reproductive Tract Cancer (Uterine, Cervical, and Ovarian Cancers)
母犬生殖道癌（子宫癌，宫颈癌以及卵巢癌）
Uterine/cervical tumors are rare in dogs, constituting just 0.3% of tumors in dogs21.
子宫/宫颈肿瘤在犬中非常少见，仅占犬类所有肿瘤的0.3%。
Spaying will remove the risk of ovarian tumors, but the risk is only 0.5'.
绝育当然可以消除卵巢肿瘤的风险，但发生卵巢肿瘤的几率仅为0.5%。
While spaying will remove the risk of reproductive tract tumors, it is unlikely that surgery can be justified to prevent the risks of uterine, cervical, and ovarian cancers as the risks are so low.
尽管绝育可以消除母犬患生殖道肿瘤的风险，但是手术可以预防子宫癌，宫颈癌以及卵巢癌的说法似乎是不合理的，因为发生这些疾病的几率本来就很小。
Urinary Tract Cancer (Bladder and Urethra Cancers) 泌尿道癌（膀胱癌和尿道癌）
An age-matched retrospective study found that spay/neuter dogs were two times more likely to develop lower urinary tract tumors (bladder or urethra) compared to intact dogs23. These tumors are nearly always malignant, but are infrequent, accounting for less than 1% of canine tumors. So this risk is unlikely to weigh heavily on spay/neuter decisions.
一项犬龄一致的回溯性研究发现绝育母犬/公犬患泌尿道肿瘤（膀胱癌或者尿道癌）的几率要比未绝育犬高2倍。并且这类肿瘤几乎都是恶性的，但发生率并不高，占所有犬类肿瘤的1%不到。因此，这项风险不会在绝育决定中占重要的比重。
Airedales, Beagles, and Scottish Terriers are at elevated risk for urinary tract cancer while German Shepherds have a lower than average risk23.
艾尔谷㹴犬，比格犬以及苏格兰㹴犬患泌尿道癌的几率较高，而德国牧羊犬患泌尿道癌的机率则要低于平均值。

Hemangiosarcoma 血管瘤
Hemangiosarcoma is a common cancer in dogs. It is a major cause of death in some breeds, such as Salukis, French Bulldogs, Irish Water Spaniels, Flat Coated Retrievers, Golden Retrievers, Boxers, Afghan Hounds, English Setters, Scottish Terriers, Boston Terriers, Bulldogs, and German Shepherd Dogs24.
血管瘤是犬类的常见癌症。它是某些犬种的主要死因之一，例如萨路基猎犬，法国斗牛犬，爱尔兰水犬，平毛猎犬，金毛猎犬，拳师犬，阿富汗猎犬，英国塞特犬，苏格兰梗犬，波士顿梗犬，斗牛犬以及德国牧羊犬。
In an aged-matched case controlled study, spayed females were found to have a 2.2 times higher risk of splenic hemangiosarcoma compared to intact females24.
一项犬龄配对的病例对照研究发现，和未绝育母犬相比，绝育母犬患血管瘤的几率要高2.2倍。
A retrospective study of cardiac hemangiosarcoma risk factors found a >5 times greater risk in spayed female dogs compared to intact female dogs and a 1.6 times higher risk in neutered male dogs compared to intact male dogs.25 The authors suggest a protective effect of sex hormones against hemangiosarcoma, especially in females.
另外一项针对心脏血管瘤风险因素的回溯性研究发现，和未绝育母犬相比，绝育母犬的风险要高5倍以上，和未绝育公犬相比，绝育公犬的风险要高1.6倍。研究者认为这是因为性激素对预防血管瘤有保护作用，尤其是对于母犬来说。
In breeds where hermangiosarcoma is an important cause of death, the increased risk associated with spay/neuter is likely one that should factor into decisions on whether or when to sterilize a dog.
对于那些血管瘤为重要死因之一的犬种来说，在决定是否要对犬做绝育手术之前，或许应将绝育会引起患血管瘤几率增加的因素考虑在内。

Hypothyroidism 甲状腺功能减退
Spay/neuter in dogs was found to be correlated with a three fold increased risk of hypothyroidism compared to intact dogs. 26.
有研究发现，和未绝育犬相比，绝育母犬/公犬患甲状腺功能减退的几率会增加3倍。
The researchers suggest a cause-and-effect relationship: They wrote: “More important [than the mild direct impact on thyroid function] in the association between [spaying and] neutering and hypothyroidism may be the effect of sex hormones on the immune system. Castration increases the severity of autoimmune thyroiditis in mice” which may explain the link between spay/neuter and hypothyroidism in dogs.
研究者认为其中的因果关系为：“和绝育所带来的对于甲状腺功能的微弱影响相比，导致价值甲状腺功能减退的更为重要的因素可能是性激素对免疫系统的影响。老鼠的阉割手术会引发严重的自身免疫性甲状腺炎。”这也许可以解释犬类的绝育和甲状腺功能减退之间的关联关系。
Hypothyroidism in dogs causes obesity, lethargy, hair loss, and reproductive abnormalities.27
The lifetime risk of hypothyroidism in breed health surveys was found to be 1 in 4 in Golden Retrievers10, 1 in 3 in Akitas28, and 1 in 13 in Great Danes29.
犬类的甲状腺功能减退会导致肥胖，嗜睡，掉毛以及生殖异常。在针对纯种犬的健康调查中发现，不同犬种一生中患甲减的几率分别为：金毛猎犬1/4，秋田犬1/3，大丹犬1/13。

Obesity 肥胖症
Owing to changes in metabolism, spay/neuter dogs are more likely to be overweight or obese than intact dogs. One study found a two fold increased risk of obesity in spayed females compared to intact females30.
由于新陈代谢的改变，和未绝育犬相比，绝育母犬/公犬更容易超重或肥胖。有一项研究发现，和未绝育母犬相比，绝育母犬患肥胖症的几率要增加2倍。
Another study found that spay/neuter dogs were 1.6 (females) or 3.0 (males) times more likely to be obese than intact dogs, and 1.2 (females) or 1.5 (males) times more likely to be overweight than intact dogs31.
另一项研究发现，和未绝育犬相比，绝育母犬/公犬患肥胖症的几率分别要高1.6倍（母犬）或者3.0倍（公犬），超重的几率分别要高1.2倍（母犬）或1.5倍（公犬）。
A survey study of veterinary practices in the UK found that 21% of dogs were obese.30
Being obese and/or overweight is associated with a host of health problems in dogs. Overweight dogs are more likely to be diagnosed with hyperadrenocorticism, ruptured cruciate ligament, hypothyroidism, lower urinary tract disease, and oral disease32. Obese dogs are more likely to be diagnosed with hypothyroidism, diabetes mellitus, pancreatitis, ruptured cruciate ligament, and neoplasia (tumors)32.
在英国兽医诊所进行的一项调研发现，21%的犬患有肥胖症。肥胖及/或超重和犬的许多健康问题都有关联。超重的犬更容易患肾上腺功能亢进，十字韧带断裂，甲状腺功能减退，下尿路疾病以及口腔疾病。肥胖的犬则更容易患甲状腺功能减退，糖尿病，胰腺炎，十字韧带断裂以及肿瘤。

Diabetes 糖尿病
Some data indicate that neutering doubles the risk of diabetes in male dogs, but other data showed no significant change in diabetes risk with neutering33. In the same studies, no association was found between spaying and the risk of diabetes.
有数据显示绝育会使公犬患糖尿病的几率加倍，但也有其它数据显示绝育不会使公犬患糖尿病的风险显著改变。在这些研究中，没有发现母犬绝育和糖尿病风险之间的关联。

Adverse Vaccine Reactions 免疫不良反应
A retrospective cohort study of adverse vaccine reactions in dogs was conducted, which included allergic reactions, hives, anaphylaxis, cardiac arrest, cardiovascular shock, and sudden death. Adverse reactions were 30% more likely in spayed females than intact females, and 27% more likely in neutered males than intact males34.
有人针对犬的免疫不良反应进行了一项回顾性定群研究，包括过敏反应，荨麻疹，过敏性休克，心脏骤停，心血管性休克以及猝死。绝育母犬发生不良反应的几率比未绝育母犬要高30%，而绝育公犬则比未绝育公犬高27%。
The investigators discuss possible cause-and-effect mechanisms for this finding, including the roles that sex hormones play in body’s ability to mount an immune response to vaccination.34
研究者讨论了该项发现可能的因果机制，包括性激素在体内对疫苗产生免疫反应中所起的作用。
Toy breeds and smaller breeds are at elevated risk of adverse vaccine reactions, as are Boxers, English Bulldogs, Lhasa Apsos, Weimaraners, American Eskimo Dogs, Golden Retrievers, Basset Hounds, Welsh Corgis, Siberian Huskies, Great Danes, Labrador Retrievers, Doberman Pinschers, American Pit Bull Terriers, and Akitas.34 Mixed breed dogs were found to be at lower risk, and the authors suggest genetic hetereogeneity (hybrid vigor) as the cause.
玩具犬和较小型犬种发生不良免疫反应的风险较高，同样还有拳师犬，英国斗牛犬，拉萨犬，魏玛猎犬，美国爱斯基摩犬，金毛寻回犬，巴吉度猎犬，威尔士柯基犬，西伯利亚哈士奇犬，大丹犬，拉布拉多寻回犬，杜宾犬，美国比特斗牛梗以及秋田犬。混种犬发生不良反应的几率较低，研究者认为是基因异构性（杂交优势）的原因。

Urogenital Disorders 泌尿生殖系统疾病
Urinary incontinence is common in spayed female dogs, which can occur soon after spay surgery or after a delay of up to several years. The incidence rate in various studies is 4-20% 35,36,37 for spayed females compared to only 0.3% in intact females38. Urinary incontinence is so strongly linked to spaying that it is commonly called “spay incontinence” and is caused by urethral sphincter incompetence39, though the biological mechanism is unknown. Most (but not all) cases of urinary incontinence respond to medical treatment, and in many cases this treatment needs to be continued for the duration of the dog’s life.40
尿失禁在绝育母犬中很常见,它有可能在绝育手术后不久即发生,或者也有可能延迟数年后才发生。不同的研究显示绝育母犬发生尿失禁的几率为4-20%，而未绝育母犬的发生机率仅为0.3%。尿失禁和母犬绝育手术之间的关联性是如此之强，以至于它通常被称为“绝育尿失禁”。其病因为尿道括约肌无能，尽管其生物学机制尚不清楚。大多数（但非全部）尿失禁症状可通过药物治疗得到改善，在很多病例中，这种治疗需要持续终生。
A retrospective study found that persistent or recurring urinary tract (bladder) infections (UTIs) were 3-4 times more likely in spayed females dogs than in intact females41. Another retrospective study found that female dogs spayed before 5 ½ months of age were 2.76 times more likely to develop UTIs compared to those spayed after 5 ½ months of age.42
一项回溯性研究发现绝育母犬发生持续尿路（膀胱）感染（UTIs）或者重复发生尿路感染（UTIs）的几率比未绝育母犬要高3-4倍。另一项回溯性研究发现在5 ½月龄之前绝育的母犬比在5 ½月龄之后绝育的母犬发生UTIs的几率要高2.76倍。
Depending on the age of surgery, spaying causes abnormal development of the external genitalia. Spayed females were found to have an increased risk of recessed vulva, vaginal dermatitis, vaginitis, and UTIs.43
根据手术时的犬龄，母犬绝育手术还会导致外生殖器的发育异常。绝育母犬患外阴凹陷，阴道性皮炎，阴道炎以及UTIs的几率会增加。
The risk is higher still for female dogs spayed before puberty.43
在青春期之前对母犬做绝育手术会导致风险增大。

Pyometra (Infection of the Uterus) 子宫蓄脓症（子宫感染）
Pet insurance data in Sweden (where spaying is very uncommon) found that 23% of all female dogs developed pyometra before 10 years of age44. Bernese Mountain dogs, Rottweilers, rough-haired Collies, Cavalier King Charles Spaniels and Golden Retrievers were found to be high risk breeds44. Female dogs that have not whelped puppies are at elevated risk for pyometra45. Rarely, spayed female dogs can develop “stump pyometra” related to incomplete removal of the uterus.
据瑞典（在瑞典母犬很少做绝育手术）宠物保险数据显示，有23%的母犬在10岁之前罹患子宫蓄脓症。伯恩山犬，罗威那犬，粗毛柯利犬，骑士查理王小猎犬以及金毛寻回犬为发病几率较高的犬种。从未生育过的母犬患子宫蓄脓症的几率会大大增高。绝育母犬偶尔可能因子宫摘除不完全而发生“子宫残端蓄脓”。
Pyometra can usually be treated surgically or medically, but 4% of pyometra cases led to death44.
子宫蓄脓症可通过手术或服药进行治疗，但是有4%的子宫蓄脓症会导致犬死亡。
Combined with the incidence of pyometra, this suggests that about 1% of intact female dogs will die from pyometra.
结合子宫蓄脓症的发生率，这个数据说明大约有1%的未绝育母犬会死于子宫蓄脓症。

Perianal Fistulas 肛周瘘管
Male dogs are twice as likely to develop perianal fistulas as females, and spay/neutered dogs have a decreased risk compared to intact dogs46.
公犬患肛周瘘管的几率是母犬的2倍，而和未绝育犬相比，绝育母犬/公犬患肛周瘘管的几率则会降低。
German Shepherd Dogs and Irish Setters are more likely to develop perianal fistulas than are other breeds.46
德国牧羊犬和爱尔兰塞特犬比其它犬种更容易患肛周瘘管。

Non-cancerous Disorders of the Prostate Gland 非癌性前列腺疾病
The incidence of benign prostatic hypertrophy (BPH, enlarged prostate) increases with age in intact male dogs, and occurs in more than 80% of intact male dogs older than the age of 5 years47. Most cases of BPH cause no problems, but in some cases the dog will have difficulty defecating or urinating.
未绝育公犬随着犬龄的增加，良性前列腺肥大（BPH，前列腺增大）的发生机率也随之增加。80%的未绝育公犬在5岁以后都会发生前列腺肥大。大部分的BPH不会引起问题，但在某些病例中患犬会发生排便或者排尿困难。
Neutering will prevent BPH. If neutering is done after the prostate has become enlarged, the enlarged prostate will shrink relatively quickly.
绝育可以预防BPH。如果在前列腺肥大之后进行绝育，则肥大的前列腺会迅速缩小。
BPH is linked to other problems of the prostate gland, including infections, abscesses, and cysts, which can sometimes have serious consequences.
BPH会引起前列腺的其它问题，包括感染，脓肿，囊肿，这些有时会引起严重后果。

Orthopedic Disorders 骨科疾病
In a study of beagles, surgical removal of the ovaries (as happens in spaying) caused an increase in the rate of remodeling of the ilium (pelvic bone)48, suggesting an increased risk of hip dysplasia with spaying.
一项针对比格犬的研究发现,手术摘除卵巢(正如母犬绝育手术所做的) 会导致骼骨(即盆骨)的重塑, 提示母犬绝育手术会增加患关节发育不良的几率。
Spaying was also found to cause a net loss of bone mass in the spine 49.
此外还发现母犬绝育手术会导致脊髓骨质减少。
Spay/neuter of immature dogs delays the closure of the growth plates in bones that are still growing, causing those bones to end up significantly longer than in intact dogs or those spay/neutered after maturity50. Since the growth plates in various bones close at different times, spay/neuter that is done after some growth plates have closed but before other growth plates have closed might result in a dog with unnatural proportions, possibly impacting performance and long term durability of the joints.
对发育未成熟的母犬/公犬进行绝育会延缓骨骼生长板的闭合，使生长板继续生长，导致这些骨骼最终比未绝育犬或者在发育成熟之后再绝育的母犬/公犬的骨骼明显增长。由于不同骨骼的生长板闭合的时间不一致，如果在进行绝育手术时有些生长板已经闭合，而有些还未闭合，就有可能导致犬的骨骼比例不正常，从而很可能影响关节的功能以及长期的耐用性。
Spay/neuter is associated with a two fold increased risk of cranial cruciate ligament rupture51. Perhaps this is associated with the increased risk of obesity30.
母犬/公犬的绝育会使前十字韧带断裂的几率增加2倍。这种情况也许和肥胖的几率增加有关。
Spay/neuter before 5 ½ months of age is associated with a 70% increased aged-adjusted risk of hip dysplasia compared to dogs spayed/neutered after 5 ½ months of age, though there were some indications that the former may have had a lower severity manifestation of the disease42. The researchers suggest “it is possible that the increase in bone length that results from early-age gonadectomy results in changes in joint conformation, which could lead to a diagnosis of hip dysplasia.”
和在5 ½ 月龄以后进行绝育的犬相比，在5 ½月龄前绝育的母犬/公犬患髋关节发育不良的几率要高70%，尽管有迹象显示后者的症状严重程度可能要轻一些。研究者认为“有可能是过早切除性腺造成骨骼的增长，而骨骼增长又导致关节结构的改变，从而可能导致髋关节发育不良症状。”
In a breed health survey study of Airedales, spay/neuter dogs were significantly more likely to suffer hip dysplasia as well as “any musculoskeletal disorder”, compared to intact dogs52, however possible confounding factors were not controlled for, such as the possibility that some dogs might have been spayed/neutered because they had hip dysplasia or other musculoskeletal disorders.
在一项针对艾尔谷梗犬的犬种健康调查中发现，和未绝育犬相比，绝育母犬/公犬患髋关节发育不良以及“任何肌肉骨骼疾病”的几率要高得多。但是，可能的混淆因素没有受到控制，例如是否某些犬做绝育的原因是因为已经患了髋关节发育不良或者其它肌肉骨骼疾病。
Compared to intact dogs, another study found that dogs neutered six months prior to a diagnosis of hip dysplasia were 1.5 times as likely to develop clinical hip dysplasia.53
Compared to intact dogs, spayed/neutered dogs were found to have a 3.1 fold higher risk of patellar luxation.54
另一项研究发现，和未绝育犬相比，在诊断出髋关节发育不良6个月前绝育的公犬发生临床髋关节不良的几率要高1.5倍。而和未绝育犬相比，绝育母犬/公犬发生膝盖骨易位的几率要高3.1倍。

Geriatric Cognitive Impairment 老年认知障碍
Neutered male dogs and spayed female dogs are at increased risk of progressing from mild to severe geriatric cognitive impairment compared to intact male dogs55. There weren’t enough intact geriatric females available for the study to determine their risk.
和未绝育犬相比，绝育公犬和母犬发生轻度到重度老年认知障碍的几率会增高。但没有获得足够的未绝育老年母犬来进行确定几率的研究。
Geriatric cognitive impairment includes disorientation in the house or outdoors, changes in social interactions with human family members, loss of house training, and changes in the sleep-wake cycle55.
老年认知障碍包括在室内或者室外不辨方向；和人类家庭成员社交互动改变；居家大小便行为的改变；以及睡眠习惯的改变。
The investigators state “This finding is in line with current research on the neuro-protective roles of testosterone and estrogen at the cellular level and the role of estrogen in preventing Alzheimer’s disease in human females. One would predict that estrogens would have a similar protective role in the sexually intact female dogs; unfortunately too few sexually intact female dogs were available for inclusion in the present study to test the hypothesis”55
研究者声称“这项发现和目前以下的研究是一致的，即睾丸素素和雌激素在细胞水平上对神经的保护作用以及雌激素在预防女性患老年痴呆症方面的作用。我们可以预计雌激素在未绝育母犬身上也起到类似的保护作用。遗憾的是，在现有的研究中没有未绝育母犬得样本太少，无法对这个假设进行测试。”

CONCLUSIONS 结论
An objective reading of the veterinary medical literature reveals a complex situation with respect to the longterm health risks and benefits associated with spay/neuter in dogs. The evidence shows that spay/neuter correlates with both positive AND adverse health effects in dogs. It also suggests how much we really do not yet understand about this subject.
对兽医医学文献客观的阅读揭示了和母犬/公犬绝育手术相关的长期健康风险和益处。证据显示绝育既会给犬带来正面的健康影响，同时也会带来负面的健康影响。它同时也让人们意识到在这个问题上认识的匮乏。
On balance, it appears that no compelling case can be made for neutering most male dogs to prevent future health problems, especially immature male dogs. The number of health problems associated with neutering may exceed the associated health benefits in most cases.
For female dogs, the situation is more complex. The number of health benefits associated with spaying may exceed the associated health problems in many (not all) cases. On balance, whether spaying improves the odds of overall good health or degrades them probably depends on the age of the dog and the relative risk of various diseases in the different breeds.
总之，似乎无法举出令人信服的案例可以说明对大多数公犬，尤其是发育未成熟的公犬，进行绝育是可以预防将来的健康问题。在大多数案例中，公犬绝育所引起的健康问题可能要超过所带来的健康益处。而对于母犬，情况则更为复杂。在许多案例（非所有案例）中，母犬绝育所带来的健康益处则可能要超过健康问题。总的来说，母犬绝育是会提高总体健康几率还是降低健康几率可能要取决于犬的年龄以及不同犬种发生各种疾病的相对几率。
The traditional spay/neuter age of six months as well as the modern practice of pediatric spay/neuter appear to predispose dogs to health risks that could otherwise be avoided by waiting until the dog is physically mature, or perhaps in the case of many male dogs, foregoing it altogether unless medically necessary.
传统的绝育时机（6个月）以及现代在幼犬时期绝育的做法有可能使犬更容易罹患疾病，而这些疾病原本是可以避免的，如果1）等犬生理成熟之后再绝育；或者 2）对于众多的公犬来说，干脆不做绝育，等到医疗必要时再做。

The balance of long-term health risks and benefits of spay/neuter will vary from one dog to the next. Breed, age, and gender are variables that must be taken into consideration in conjunction with non-medical factors for each individual dog. Across-the-board recommendations for all dogs do not appear to be supportable from findings in the veterinary medical literature.
绝育所带来的长期的健康风险和益处视不同的个体而不同。犬种，年龄以及性别都是可变因素，需作为每一只狗的非医学因素考虑在内。兽医医学文献的研究结果不支持一刀切地对所有宠物犬做出关于绝育方面的建议。

REFERENCES/参考文献 (略)

狗狗绝育的好处和坏处