Polycystic kidney disease

My delightful 4.5 year old girl, Charlee, was just diagnosed a few hours ago with PKD.  Here's what happened.  She'd seemed a little lethargic the past couple days so I was going to take her to the vet anyway.  But I picked her up (I hold both my fuzzies often) and her abdomen was misshapen and hard.  I swear, it wasn't like that until today, or I honestly have zero idea how I couldn't have felt it earlier since I'm always poking and prodding them for abdominal abnormalities.  Took her immediately to the vet who took an x-ray and said PKD.  He showed me how her kidneys (or the cysts on them...?) were so large that they were taking up her entire abdomen and compromising her intestines.

Is this worth getting a second opinion or should I just bite the bullet and put her down?  He said she's got maybe a week, and I don't want her to suffer a second longer than necessary.  But if it's something treatable, shouldn't I try?

I'm really sorry.  From what I've read, all you could do is treat symptoms, but since it's genetic, there's not much to be done as for cure.  I feel for you.

THE DOOKS OF HAZARD