Why did my rat pass on?? :(

Question
Im not sure how old he was b/c i got him from a friend who had him for quite sometime.my cat didnt get him cause i caught my cat jus in time.he lived alone in his cage.there was absolutely NUTHING he couldve got stuck on.could he have been bleeding inside n it came out from his rectum?or could it have been old age?im really curious to know y the poor lil guy passed.he was bleeding a bit from his nose for a lil while since i got him but i didnt think nething of it.maybe he was sick?? i really wish i knew.please help me.
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-----Question-----
My rat jus passed away, i found him tonite dead in his cage,my question is"is it my fault?" he had food, n water..he was fine a few days ago.my cat went up to the cage but i got him down n the rat was fine,the rat was a male, and when i found him dead his testicles were gone...what does that mean? and why was there blood all over his cage but he had no wounds on his body?i have so many questions to ask but i wont take up to much of ur time.I hope to c a response from u very soon, and then iwill ask more questions...Thanks
-----Answer-----
How old was your rat? Did he had another partner living with him? I don't think it's your fault that he died. Is there anything that he could have gotten stuck on. Are you sure your cat didn't get to him? I think your cat may have gotten to him.

Answer
It sounds like he was bleeding internally and coughing up blood. He had to have had sometype of hemmorage inside his body or something for him to bleed like that yet have no cuts or wounds. I've been looking for a disease that causes this but have yet been able to find one. It's not your fault I know for sure because nothing like this could be your fault. I can't explain why his testicles are missing.
This is truly a big mystery to me and I can only give you what I know, maybe something had been wrong with him for a long time and no symptoms showed and then something might have ruptured inside him causing him to bleed to death. This is the only thing that I can think of.