Hello and thanks for researching this very important question!
Older female dogs can develop a number of medical conditions that result in weakness of the bladder nerves and muscles, or can cause confusion about where to "go".
These conditions include (but are not limited to):
1) Canine Cognitive Dysfunction Syndrome--a shortage of brain neurotransmitters
www.cdsindogs.com
2) Low estrogen level--from being spayed, or no longer producing estrogen in geriatric ovaries
3) Kidney/liver disease
4) Diabetes (mellitus or insipidus)
5) Bladder infection and/or stones in the bladder
http://www.petplace.com/dogs/urinary-incontinence-in-dogs/page1.aspx
***Please have this dear pet examined by a veterinarian who can properly diagnose and provide treatment(s) for this problem as soon as you are able.***
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