How much phosphorus is too much?

So, I posted on a previous thread that my cat had passed on from CKD.




He had always eaten a balanced diet even up to the end, with one exception: one of his last meals had a phosphorus count of 1.48%  Just about everything else he ate ranged between 0.50% to 0.9% (is that the right way to measure it?)



Anyway, my worry was originally that there may have been too much protein, but the answers I received seemed to indicate that wasn't the case, much to my relief.  But now, I'm worrying that the phosphorous from his one-time of eating this particular food may have done it. And it wasn't even that much food, he only ate about a tablespoon's worth (it was dry food)



Also, is 0.50% to 1.48% a small difference or is it a major, night-and-day difference?  I'm really hoping that it was just a bad coincidence; that his kidneys were just ready to go at that point anyway and that it wasn't a single miscalculation that caused everything to come crashing down all at once.

First off I'm sorry for your loss.

The answer is no. No way. One meal or even one day of higher phosphorus is not going to send his kidneys over the edge.

Phosphorus is an accumulating ingredient.

Okay, good to know. Thank you for the reply and for the condolences.

lol I always knew one day that I'd meet somebody on this board with the username "Catwoman".

My condolences for your loss. 

I was actually asking the same question as you about a week ago. I found out that what catwoman said was right: Phosphorus accumulates. It shouldn't be no higher than 6 mg/dl. I go by what I find in this food chart created by Dr. Pierson. She uses mg/100 kcals, and so I have no idea what the conversation of that might be but I tend to stay away from anything above 300 mg/kcal. 

Absolutely, one meal won't make a difference. I found out (a year ago today actually) that my Sara had acute on chronic renal failure, and a very long week later, after assist feeding every day, she decided to eat on her own. And she picked the most phosphorus-laden food I had (which were leftovers from one of my other cats). 2.5% phos!! Vet said if she's eating, that's what matters. Phos binders help with that! Not sure if your kitty was on those or not.

The high phos is a result of the kidney disease, not the other way around. High phos will make them feel bad, but it's ultimately the kidneys shutting down that will take them in the end. Or in some cases lack of eating, though that doesn't sound like that was an issue.

And very sorry for your loss

Thanks for the replies and condolences!

My vet had recommended a phosphorous binder (Epakitin) for my cat several months ago, along with Hills K/D food, yet when his bloodwork came back during that time, his phosphorous was almost right in the middle of the normal range.  Combine that with the normal creatinine and SDMA levels, along with an elevated BUN count, and it seemed like he had more of a problem with chronic dehydration rather than proper kidney disease.  This made more sense to me at the time, given that he had a violent vomiting episode after food poisoning a couple of years back.

I asked the vet about this and he didn't have a straight answer to give me.  He was more the "this is what you should do, I shouldn't have to explain it" sort of vet, which never sat well with me.  Even other vets I asked couldn't clarify this for me, but at least one of them did say that given the supposed early stage of my cat's kidney disease, that it would be somewhat premature to give him the K/D diet.  I didn't want to risk giving him anything that he didn't need due to a possible misdiagnosis.  The whole thing just got so confusing!  What further made me doubt my vet was when my vet's office prescribed the binder to me, they wrote "EpiKAT" instead of "Epikitin".  They can't even get the name right?  Come on!  If I ever get another cat (which I probably will at some point), I'm finding a new vet.