Blood in 6 year old in spayed females urine

Question
Cotton is my unspayed bunny. She is 6 years old and has recently starting having blood in her urine. Turns out her uterus is dialated with fluid and blood. Anti-biotics aren't seeming to help. Her vet has ruled out an infection by testing her urine. He says she needs to be spayed but he isn't advising me to do that b/c of her age. He says within a few days I need to either decide to have her put to sleep or risk the spay surgery b/c it isn't good for her to remain this way. I'm afraid to try the spay b/c what if she dies during it... and I hate to put her to sleep when she isn't in pain and is happy and pretty much healthy otherwise. It isn't every time she urinates but it's enough to be a concern. I should've had her spayed when she was younger. I didn't understand the importance of it back then b/c she has been my first rabbit, and I didn't intend to ever have her around any other bunnies so I wasn't worried about accidental litters.
Have you ever experienced this kind of problem? What happens if left untreated? Does the bleeding just get worse and lead to pain and discomfort? I have read this... http://www.rabbitnetwork.org/articles/spay.shtml
Wouldn't it be putting her through too much to even try the spay surgery? But wouldn't it be awful to just take my happy lil' bunn in to be put to sleep? Both options are awful.

Answer
Hi Ginger,

While it is not an easy decision it basically comes down to having her spayed or she will probably die from the infection or possibly uterine cancer.  We have all of our rabbits spayed regardless of their age.  It is just the smart thing to do.  Yes there is a chance that she could die from surgery but the chance that she could die from cancer is much larger.  

I wish I could make your decision for you but I can't.  I hope this information helps you.

Pam