Hi there and thank you for your question. My name is ***** ***** I am a licensed, internship-trained veterinarian with 11 years experience in general medicine and emergency and critical care medicine and I would be happy to assist you. Please be patient as there may be slight delays in responses as I research your pet's issue.
I hate to be the bearer of bad news, but this is urine. It would and could only be urine. And when spayed female dogs leak urine, it is almost always when they are resting or sleeping. In about 5% of female dogs who are spayed, eventually they will develop spay-induced incontinence. This shows up as leaking urine when sleeping and resting. It can start slowly with just a few instances, and can progress to happening daily. The good news is that it is easily treatable with medication from your vet. The other possibility is that she has a urinary tract infection, and that is causing the sudden leakage. I recommend seeing your vet for a urinalysis to make sure there is no evidence of a UTI, and if all is normal, then your vet can prescribe the anti-incontinence medication as a trial to see if it helps.
Often, leaked urine does not smell strongly as we would expect it would, and it often seems to have no odor, so I can completely understand your confusion. But I can assure you that urine is what it is.
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