A few months ago he was having trouble peeing, and we took him into the emergency vet then because our vet was closed. He wasn't blocked (which was our fear, that being common and very dangerous in older male cats) and some sub-Q and antispasmodics cleared him up in a day or so. X-rays from the first incident showed some small kidney stones but nothing migrating. It was chalked up to idiopathic (i.e., no particular cause) cystitis.
But then it happened a couple more times. Last time he was in he got another set of X-rays, which showed his left kidney significantly enlarged and low but smooth, and a full workup, which showed high urea and creatinine levels in his urine, a classic sign of chronic renal failure. On top of all that he's been losing weight despite having a good appetite; he's down around 8.5 lbs now. He was never a big cat but he's pretty boney at that weight. "Supermodel cat", our regular vet called him.
The internal medicine vet, Dr. Norris at the VEC, asked a lot of good questions this morning and walked me through the X-rays and so on, and explained what we know and what we don't: that kidney failure is common in cats, especially purebreds, although at 13 Rasha's towards the young side of age-related kidney problems; that the stones aren't a big concern if they stay in the kidneys, but if they start migrating it can cause a problem fast, but that's not the problem here; that since cats (and humans) can get by on very little kidney, showing elevated levels is often a sign of significant damage; and that neither the cystitis nor the kidney problem really explain the weight loss.
And on top of that I've learned on my own that Birmans are predisposed to renal dysfunction.
He's there now awaiting his ultrasound (and resulting shaved belly -- can you picture this shaved?).
He's still a happy cat, hanging out in the window and snuggling with us and eating normally and generally being his usual bratty self, but I'm worried that he's starting to wear out with age. Poor little kitter. Cross your fingers for us, folks.