Cat has passed away and had black stuff coming from its mouth...what could that be?

Question

I have a friend/co-worker who went home yesterday and found her cat had passed. The cat was previously peeing in random places and had taken the cat to the vet and they said nothing was physically wrong and suggested that the cat could be suffering from dimentia. (it was 12) Anyway, the cat was found with black stuff coming from its mouth. Has anyone else experienced such a thing. I suggested that the cat may have ingested some sort of poison but I was just wondering if anyone else heard of such a thing. Can't change what happened but she has 2 other cats that hopefully are safe.

Answer 1

That could have been old blood from an aneurysm or some other stomach or lung problem.  When blood is old it goes from red to black.

Answer 2

My guess would be it was either dried blood or something that was poisonous to the cat.  If it was dried blood, it could have been from internal bleeding.  Blood will naturally turn dark.  Your friend should make sure there is no mouse bait such as D-Con or anything like that somewhere in her home.  Even if the cat didn't eat the actual poison, it could have eaten a mouse or rodent that had injested the poison, thus poisoning the cat.  If the cat was allowed to go outside, it could have got poisoned by someone who put rodent bait out in an effort to kill cats or rodents.