A friend of mine who is a medical resident (human medicine, not animal) had the following analysis:
Nobody has replied to my original thread but there's alot of analysis below which may be useful to others...
Here is my interpretation of the medical issues:
The famotidine and the diet change are reasonable measures to take. She could have just had a gastroenteritis which aggravated her stomach and caused the vomiting.
If the vomiting persists, it's a whole other story; it could still be infectious, but there's a whole list of other things which would require more tests to assess.
If she is no longer vomiting though I really wouldn't worry about it. If she continues to vomit, there are other things you can check (liver function, etc.) but I don't think that is necessary at this point.
2) The kidneys
I'm not sure if she has chronic kidney disease. Usually you need to have renal impairment for ~3 months before declaring that.
It seems her creatinine has gone from 216 to 182 over a short time, indicating some degree of renal recovery. I wouldn't be surprised if you rechecked it in a while and it normalizes.
It's possible that the excessive vomiting caused her to be dehydrated which led to the renal impairment. Now that she's not vomiting and that she's drinking well, she isn't dehydrated and her kidneys are perfused better, which is why the creatinine is coming down.
If that's the case, I would expect her kidneys to recover fully.
They indicate that the specific gravity is normal which favours renal disease; I don't know if it's the same for cats but in people we don't really use that value at all.
The most common causes of chronic kidney disease are diabetes (which apparently she doesn't have) and hypertension (the BP was 140; in a human that's a little elevated, probably not high enough to give renal impairment, but maybe in a cat that value is normal)
She said maybe there was suggestion of a urine infection (WBCs in the urine) however the culture was negative. I don't think she has a pyelonephritis; the culture would have grown something and she would be much sicker. Her temperature was 38.2...in a human that is a fever, but I'm not sure of what to make of that in a cat.
The fact that there's no protein in the urine (UPCR was 0.1) is reassuring and suggests only very mild renal impairment.
I think the renal diet is reasonable (although in humans there is no evidence that that is even necessary).
The only curious thing on the ultrasound were those small calcification they noticed. In renal disease, the first metabolic signs are often hyperparathyroidism leading to calcium phosphate depositions in the kidney.
The only thing you could check are the calcium and phosphate levels in the blood if that wasn't already done. If the phosphate levels are high, there are medications for her which might be useful.
In summary, for her kidneys, I would recommend the following:
1) Don't worry about it; the creatinine is not that elevated and is coming down, theres is no proteinuria (all reassuring signs), etc.
2) Recheck the creatinine at the next visit.
If her creatinine is still high, in a human we would tend to look for causes of the renal failure (since there is no definite hypertension or diabetes). I don't know how much it would change the management in a cat, though, and it would be very expensive...
In any case, we would consider treatments aimed at preventing progression of the disease, such as an ACE inhibitor (to protect the kidneys), bisphosphonates (for skeletal protection), calcium/vitamin D supplementation, etc.
At the next visit, you can ask the vet about those things.
3) A small thing...lymphopenia
The vet says this is related to stress? That doesn't really make sense. How lymphopenic is she? I'm not sure what to make of this; you may want to get it repeated to make sure it has resolved.
I hope this is helpful and that she feels better.