hind leg paralysis in male rat

Question
Hello

I was wondering if you would have any idea what is wrong with my rat. He is a 1 and 1/2 year old male, albino and untill last night was fine. I fed them last night and noticed that he was really slow comming out of his house. When he did come out he looked 'puffed up' and hunched over, but he is eating and drinking fine. His litter mate is also fine.
I rang the emergency vet and they said wiat until tomorrow to bring him in.
This morning he was having trouble walking, only his back legs are affected (his tail is fine) it is like he is dragging them a bit. I took him to the vet and she presribed him pain killers as she thought it was an injury from falling in his cage. His heart and breating were fine but he did seem in pain on his abdominal region.  
He also has some blood/brown mark around his nose (but he does sometimes have his anyway from scratching it).
Do you have any idea on what could have happened to him and what I can do to help him, I really do not want him to be in pain or suffer. I would really appriciate any advice. Thank you

Answer
Please refer to my website, Sandyscrittercity.com, and refer to the page on hind leg paralysis which can be found on the page with the topic about caring for elderly rats, and also so you know that the brownish discharge you see is NOT blood, check out the page on bloody eyes and nose so you will understand what is going on.

I want you to notice if his tail is able to lift up and be held up and also if its cold to the touch. What kind of pain killers did the vet give him?  If it is metacam/meloxicam, please read up on that as well on my site as this is NOT good for rats and is nothing better than advil.