serious question..what would cause anal bleeding in a hamster?

the hamster im asking about is dead now, she lived 3-4 years.
about 2 or 3 weeks before she died i picked her up and her butt was bleeding EVERYWHERE!
i gave her a bath and i couldnt find any cuts or bites on her, was she actually bleeding out of her butt? is it possible she got colon cancer or something?
she also had fleas pretty bad for a while (the dog spread them everywhere) could they possibly bite her THAT bad??
it never happened before or after that time but it really freaked me out.. ive never heard of that happening before.