Phosphorus question for the CRF/CKD folks

Ruby had some blood & urine tests last week. So far, things seem to be holding steady. Her USG was 1.020, which is where it's been for the last few tests. BUN is down to 24 (was 36 in November), CREA is the same at 2.0. What seemed weird to me is that her phosphorus level has dropped, too, without the use of binders. It's 2.4, which our lab says is too low. In November it was 3.6 (even then it was on the low end). We did switch from Fancy Feast to Friskies SpecialDiet.
Do I need to worry about it being that low?

(We went in because of a stomach bug. They gave her some sub-q fluids at the time but said she wasn't super dehydrated or anything)

 

I found a good article for you to read: http://www.petmd.com/cat/conditions/endocrine/c_ct_hypophosphatemia

Apparently, hypophosphatemia has been known to occur during insulin therapy. Did your vet say the thought was that your kitty was early CKD? Because, with the BUN and creatinine coming down so quickly, it's entirely possible the stomach bug was the entire reason for the elevated numbers.

Anyway, according to the food chart, in general, the Friskies special diet has 1/2 the amount of phosphorus as the Fancy Feast. Depending on your kitty's calcium levels, can you ask your vet about supplementing with vitamin D? Or, maybe you can even go back to the Fancy Feast, as surely, that will bump up the phosphorus. But, you do need to do something, because too low can be problematic too.

This is a link to Dr. Pierson's food chart if you don't have it: http://www.catinfo.org/docs/Food Chart Public 9-22-12.pdf

DZ and Sarah

 

Thanks for the link. Ru isn't currently on insulin. She's OTJ (her last shot was in April). The vet diagnosed her with early CKD in September. She wasn't showing any symptoms, it was found on a routine blood test. For the most part, all of her tests have been consistent until this one with the drop in BUN and phosphorus. There is a tab on her spreadsheet called Ruby's Lab Tests (link in signature) that has all of her tests with the dates & results.

 

The more important thing than the level of phosphorus is the phosphorus:calcium ratio. If the phosphorus gets to low in relation to the calcium, then the body will start to store the extra calcium in organs like the heart and that can cause damage to those organs. This is how our vet explained this when I was concerned about our non-CKD cats eating the low phosphorus. The good thing is she said that, though it is absolutely possible, she has never seen it happen in a cat, only seen it in dogs in her years of practice.

I would maybe switch to something in the middle food-wise, not going back to something as bad as Fancy Feast pates (appear to be the worst offenders when it comes to phosphorus), yet move out of the low phosphorus foods too.

 

She's eating Friskies Special Diet Beef & Chicken, which I think is at 242 for phosphorus. If I remember correctly, the FF is in the 500s. We tried every low carb/mid phos food we could find and this is the only one that she & our civvie would both eat with any regularity. They rejected everything else. Seeing how little most of her tests have changed, I think its ok to stick with it. Ru's CREA and BUN levels have actually been roughly the same since her FD diagnosis in December of 2011. The vet only mentioned it in September 2012.

ETA...her Calcium is on the low end of the normal range for our lab. She tested at 9, normal is 8.9-11.7.

 

Er, duh. Sorry I missed the giant, neon green OTJ in your signature the first time around. Sheesh.

Anyway, yes, I agree with Melaine about finding a food for middle of the road phosphorus. Actually, she provided some good insight on many areas.

So, please do ask your vet about supplementing with some vitamin D in the meantime, as apparently, it is depleted in low phosphorus cases. If you have any Fancy Feast left over, maybe you can plop a TBS of that on top of the existing food but keep it off your Civie-cat's meal.

DZ and Sarah

 

Our civvie's numbers are on the low end of things too...BUN - 22, Crea - 0.9, Phos - 2.9

I just hate to change up their diet too much. Their bellies don't handle it well. Maybe I'll put another call into the vet and ask them about it again. They've learned that I keep a record of all of the test results so I can see trends over time. Every time I walk in there with a stack of paper, they give me the eye roll. :smile: