On the positive side, neutering male dogs
• eliminates the small risk (probably <1%) of dying from testicular
cancer
• reduces the risk of non-cancerous prostate disorders
• reduces the risk of perianal fistulas
• may possibly reduce the risk of diabetes (data inconclusive)
On the negative side, neutering male dogs
• 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.
• increases the risk of cardiac hemangiosarcoma by a factor of 1.6
• triples the risk of hypothyroidism
• increases the risk of progressive geriatric cognitive impairment
• triples the risk of obesity, a common health problem in dogs with
many associated health problems
• quadruples the small risk (<0.6%) of prostate cancer
• doubles the small risk (<1%) of urinary tract cancers
• increases the risk of orthopedic disorders
• increases the risk of adverse reactions to vaccinations
On the positive side, spaying female dogs
• if done before 2.5 years of age, greatly reduces the risk of mammary
tumors, the most common
malignant tumors in female dogs
• nearly eliminates the risk of pyometra, which otherwise would affect
about 23% of intact female
dogs; pyometra kills about 1% of intact female dogs
• reduces the risk of perianal fistulas
• removes the very small risk (0.5%) from uterine, cervical, and
ovarian tumors
On the negative side, spaying female dogs
• 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
• 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
• triples the risk of hypothyroidism
• increases the risk of obesity by a factor of 1.6-2, a common health
problem in dogs with many
associated health problems
• causes urinary “spay incontinence” in 4-20% of female dogs
• increases the risk of persistent or recurring urinary tract
infections by a factor of 3-4
• increases the risk of recessed vulva, vaginal dermatitis, and
vaginitis, especially for female dogs
spayed before puberty
• doubles the small risk (<1%) of urinary tract tumors
• increases the risk of orthopedic disorders
• increases the risk of adverse reactions to vaccinations