how the tides have changed

it's amazing how you can go from a complete natural high to feeling incredibly low and sad in an instant. i can't remember the last time i cried and in fact, have never seen ken cry - until yesterday.
our drastic mood change was brought on by some sad news - news that will make this next little while rough and challenging.
our dog pingu has been littered with health problems ever since we brought her home - hernias, eye infections, ear infections, face fungus - yet through it all she's persevered and remained a happy puppy. however, within the last week she's been having a hard time holding her back legs up and they seem to give out on her, especially when she goes to the bathroom. thinking (and hoping) it wasn't anything serious we decided to just keep a close eye on it and hope she'd get better.
sadly, that hasn't been the case. her condition has worsened over the week and yesterday i had to bring her to the vet to get it checked out. after leaving her there for xrays, the vet wasn't optimistic about her condition and speculated that it was a form of degenerative disc disease - something that, if not treated immediately could worsen and (worse yet) could reoccur in a more severe form causing paralysis and immediate (and costly) surgery in guelph.
after xraying her, the results were worse than anticipated. the vet said she has never seen a case like this, nor have any of her colleagues. my poor darling has been suffering with many abnormalities on her spine - extra boney growth, compressed discs and several abnormal vertebraes. basically, something that can't be repaired with surgery even if we had the money for it.
at this point we're not sure what to do and it's been rough watching her suffer and really strain to go to the bathroom.
when do you get to that point when enough is enough? how do you make that decision? i've only once ever had to put a dog down with my mom and she was VERY ill and we knew that it was better for everyone at the time.
this case is different. pingu is our first dog together, ken's first dog ever. she is the perfect pet despite all her health problems. and worse yet, she's family.
we never anticipated having to make this difficult decision only a year and a half into her young life. she hasn't had an easy go and by the sounds of it, this spinal issue is something she's grown up with and adapted to.
at the moment we're just trying to keep her comfortable - that's all we can do. her xrays have been sent to a radiologist in guelph who specializes in unique/abnormal cases so hopefully we can get some answers from him next week and go from there.
we're hoping for a miracle....