Older Dog Bleeding from Vagina

Question
Hi,
My 13 year old st. bernard mix female is bleeding from her vagina. She is at full life, isn't very steady on her back legs anymore, has non-cancerous tumors on her body, but started bleeding from her vagina a couple hours ago. It was bright red and was dripping down her leg. It seems to have slowed down now. She is eating, drinking and going to the bathroom normally. I have a pair of my husband's underwear on her and cut a hole for her tail. She is sleeping comfortably right now and acting normally. I plan to take her to the vet first thing in the morning. Any idea what it can be?

Answer
Pretty hard to know over the internet. Is she spayed? It could be just a vessel ruptured but if she isn't spayed she could be developing a uterine infection.

Since the vestibule that is where her vagina is located also holds the entrance to her urethra it's very possible that she has a bladder infection, kidney infection,or a foreign body in there or even a tear.

The vet will be better able to assess this since he/she can examine her.
I do hope that it is nothing serious at this point, although 13 is very old for a St. Bernard, even a mix!
I am glad that you are taking her in tomorrow morning.