Hypophosphataemia in cat with CRF and hypoT4

Re: Hypophosphataemia in cat with CRF and hypoT4

mariette asselbergs — Sun, 17 Nov 2013 00:18:51 GMT

BSAVA Manual of canine and feline clinical pathology p 434 Differential diagnosis of hypophosphataemia:

Hyperparathyroidism

Malignancy associated hypercalcaemia with release of PTH-gammaP

Hypovitaminosis D (intestinal malabsorption, dietary)

Following insulin therapy

Re-feeding syndrome

Prolonged anorexia

Fanconi syndrome

Maybe try to test for parathyroid hormones?

Mariette

Re: Hypophosphataemia in cat with CRF and hypoT4

Tiago Henriques — Fri, 15 Nov 2013 12:54:13 GMT

Hi!

It's rare but could be renal tubular acidosis.

Re: Hypophosphataemia in cat with CRF and hypoT4

John Flynn — Fri, 15 Nov 2013 10:40:47 GMT

[quote user="shanley barber"]I have looked back at my notes, I have run in house bloods twice (mid October and 4 d ago) since starting the hills kd+Tumil K, and repeated the first in another branch, same blood, different type of machine, and all three have been we'll below normal. We ran a quality control soon after this result, which suggested our results were fine. Prior to starting this diet, the Phos was normal. He is certainly hyperthyroid, he is currently on 5 mg Carbimazole daily. I ran a t4(external) at the same time as drawing the bloods 4 d ago, and it was 24 nmol/l. USG mid Sep was 1.010, at the same time as mild azotaemia, hence starting the Kd. I hear what you are saying about not needing the Phos reduced diet, John, I think stopping it and rechecking the urea/crea/Phos is probably the best plan. I feel that a spurious result is unlikely, considering the number of times I have repeated it, on separate occasions! To make matters more complicated, the owners are both GPs[/quote]

Sounds frustrating!

If they've been feeding k/d exclusively then even just letting the cat have a bit more variety might be enough to give you a phosphorous nearer to what you expect. (might be less frustrating to let the cat continue to eat some pouches of k/d and then you can always just increase the amount of this fed at a later date if kidenys deteriorate... it can be hard introducing these foods so if is eating it now that would be one argument not to withdraw totally)

Re: Hypophosphataemia in cat with CRF and hypoT4

shanley barber — Thu, 14 Nov 2013 21:13:58 GMT

I have looked back at my notes, I have run in house bloods twice (mid October and 4 d ago) since starting the hills kd+Tumil K, and repeated the first in another branch, same blood, different type of machine, and all three have been we'll below normal. We ran a quality control soon after this result, which suggested our results were fine. Prior to starting this diet, the Phos was normal. He is certainly hyperthyroid, he is currently on 5 mg Carbimazole daily. I ran a t4(external) at the same time as drawing the bloods 4 d ago, and it was 24 nmol/l. USG mid Sep was 1.010, at the same time as mild azotaemia, hence starting the Kd. I hear what you are saying about not needing the Phos reduced diet, John, I think stopping it and rechecking the urea/crea/Phos is probably the best plan. I feel that a spurious result is unlikely, considering the number of times I have repeated it, on separate occasions! To make matters more complicated, the owners are both GPs

Re: Hypophosphataemia in cat with CRF and hypoT4

John Flynn — Thu, 14 Nov 2013 19:32:10 GMT

[quote user="shanley barber"]

Yes, I meant hypERthyroid, not hypOthyroid, duh!

Calcium is within normal limits (2.6 mmol/l), this has been consistent, prior to and after the sudden change in Phosphorous. I will get it checked externally.

Thank you for your help so far, everyone!

Shanley

[/quote]

Just to be sure, I'd go back over what led to the diagnosis of CKD/CRF in the first place and double check that the hyperT4 actually is well controlled.

I personally think it tricky to differentiate mild CKD from hyperT4 that's not totally "controlled"

My take on the info you've provided would be the cat most likely simply does not need a phosphorous-restricted diet?

Re: Hypophosphataemia in cat with CRF and hypoT4

shanley barber — Thu, 14 Nov 2013 17:22:32 GMT

Yes, I meant hypERthyroid, not hypOthyroid, duh!

Calcium is within normal limits (2.6 mmol/l), this has been consistent, prior to and after the sudden change in Phosphorous. I will get it checked externally.

Thank you for your help so far, everyone!

Shanley

Re: Hypophosphataemia in cat with CRF and hypoT4

Christopher Saul — Wed, 13 Nov 2013 23:24:35 GMT

[quote user="Neil Wheadon"]Interesting that all 3 of us have said get an external check on that result[/quote]

Make it 4 of us

Chris

Re: Hypophosphataemia in cat with CRF and hypoT4

Neil Wheadon — Wed, 13 Nov 2013 15:10:36 GMT

Potentially spurious, but something is ringing in my head about potassium supplementation causing decreased phospherus absorption. (Nutrition degree in prehistoric times.)

Interesting that all 3 of us have said get an external check on that result, it's way too low.

Neil

Re: Hypophosphataemia in cat with CRF and hypoT4

Kate Richardson — Wed, 13 Nov 2013 14:27:28 GMT

As Andrew said. I have only ever seen clinically significant hypophosphataemia in DKA cats. I would definitely repeat it before investigating further as I usually find its an error of some kind and not repeatable. If it is true and persistent get a haematology run including a smear for Heinz bodies even if the HCT appears normal.

Re: Hypophosphataemia in cat with CRF and hypoT4

Andrew Kent — Wed, 13 Nov 2013 14:08:00 GMT

Hi Shanley,

I would be quite worried about a phosphate that is that low as levels less than 1.0 mmol/l have been associated with haemolysis. Supplementation would be suggested at that level, but I think if the cat is bright that I would check the phosphate again (maybe externally?) to make sure it isn't a spurious result.

Is the cat definitely hypothyroid? That is exceptionally unusual in a cat so would be interested to hear a bit more about how it was diagnosed - could it be sick euthyroid?

Intestinal malabsorption would seem quite likely if it is a genuine result and so I would probably be inclined to investigate further for GI disease - any compatible clinical signs? Weight loss? Whilst the diet may not be low enough to cause it on its own if there is any problem with absorption then a phosphate restricted diet may contribute. If you can't get it any higher then you may not have a choice but to change the diet.

Is the calcium normal?

Andy

Re: Hypophosphataemia in cat with CRF and hypoT4

Neil Wheadon — Wed, 13 Nov 2013 13:00:08 GMT

I presume you mean Hyperthyroid?

The low phosperus may not be related to the CRF at all. A Canadian report http://www.ncbi.nlm.nih.gov/pmc/articles/PMC339175/ described a case of Primary hyperparathyroidism and concurrent hyperthyroidism in a cat. so the calcium would be of interest here.

My other concern is that the measured levels here are very low, is your machine OK. Phospherus is needed for ATP therefore energy, so the brightness is surprising.

Electrolyte disturbances are difficult sometimes. I had a hypokalaemic blocked cat last week. In house suggested 2.7mmol, this was checked by an external lab and it was 3.4mmol, still slightly under the reference range, so something else is happening here and awaiting T4 result as this can cause hypokalaemia too.

Neil