hyperthyroidism and azotaemia

Re: hyperthyroidism and azotaemia

Kate Richardson — Wed, 16 Jan 2013 17:12:11 GMT

[quote user="Andrew Kent"] I'm not suggesting we shouldn't control systemic hypertension, just that we shouldn't use amlodipine alone. I accept most cats will end up on both.[/quote]

That's fair enough, I probably got the wrong end of the stick there. I would be interested to know if there are studies done or being done to to assess if there is any clinical benefit to dual therapy versus lone therapy as your treatment regime is based on theory if I am understanding correctly? Not saying it is wrong, it can certainly be justified. I have managed renal cats with amlodipine alone for hypertension for a long time so would be interested to know if the renal disease progresses more rapidly than those with ace-i on board as well; its not my clinical impression, but there are so many factors to consider with these cats that it may be difficult to prove one way or another.

Re: hyperthyroidism and azotaemia

Andrew Kent — Tue, 15 Jan 2013 19:10:55 GMT

[quote user="Rajat"]

[quote user="Andrew Kent"]therefore the addition of an ACEi (which preferentially dilates the efferent arteriole) is likely to be beneficial.[/quote]

yup - I always use an ace inhibitor WITH amlodipine in cats with hypertension for this reason.. just not an Ace-I alone! thanks for the reference. I thought the more recent (not necessarily more accurate) papers showed a significantly lower incidence of hypertension in cats with CRD which is why I asked.

[/quote] There is a massive range in the different papers and most of them are referral populations so I'm not sure we have any idea of the real incidence!

Re: hyperthyroidism and azotaemia

Andrew Kent — Tue, 15 Jan 2013 19:09:46 GMT

[quote user="Kate Richardson"]

[quote user="Andrew Kent"]The work on combination management of hypertension hasn't been studied in cats but the preferential dilation of afferent renal arterioles with calcium channel blockers has been shown to increase intraglomerular pressure, therefore the addition of an ACEi (which preferentially dilates the efferent arteriole) is likely to be beneficial. There is no reason that this would not be the same in cats. So, even if you dont see massive differences in systemic blood pressure with the ACEi, you are likely to be having benefits on glomerular pressures. Otherwise this may be to the detriment on progression of renal disease. [/quote]

I appreciate what you are saying, but management of systemic hypertension is just as important as mananging the renal hypertension- acute onset blindness in a cat due to retinal haemorrhage or detachment or CNS bleeds significantly impact on the cats QOL, more so I would say than theoretical progressive renal damage due to amlodipine.

[/quote] I'm not suggesting we shouldn't control systemic hypertension, just that we shouldn't use amlodipine alone. I accept most cats will end up on both.

Re: hyperthyroidism and azotaemia

Rajat — Tue, 15 Jan 2013 18:26:01 GMT

[quote user="Andrew Kent"]therefore the addition of an ACEi (which preferentially dilates the efferent arteriole) is likely to be beneficial.[/quote]

Re: hyperthyroidism and azotaemia

Kate Richardson — Tue, 15 Jan 2013 18:21:14 GMT

Re: hyperthyroidism and azotaemia

Andrew Kent — Tue, 15 Jan 2013 17:46:09 GMT

[quote user="Rajat"]

[quote user="Andrew Kent"]If you consider that around 75% of cats with CRF will be hypertensive[/quote]

Do you have a reference for this Andy?

My understanding from Uni, and repeatedly since from various sources has been Ace inhibitors in trials have only shown to benefit proteinuric cats. There was an absence of benefit in non proteinuric cats, so unless there's new lit out there, if the UPC is <0.4 there is no point in using an ace inhibitor.

I suppose one can explain human beings being put on them for something to unique to that species' physiology vis a vis cats...

Re azotemia- IMHO I don't think there is a need to get too worried about azotemia as long as the pet is eating and drinking well. If clinically impacted then worth doing something. If mild raise in urea creat then I would not worry IF the pet needed the Ace inhibitor badly.

I cannot remember the last hypertensive that responded to ace inhibition alone, people are much more sensitive to its hypotensive effects. In cats you won't get systolic BP reduction below 5-10mmHg (or so a famous cardiologist once told me in more flowery language!). Amlodipine is our furry feline's friend!

[/quote] the reference for that figure (I'd slightly mis-remembered it was 65%) comes from a JAAHA paper from 1994 (30; 564-572). Its an old paper but there has only been about 3 studies on this in cats and they differ widely, but the point is that it can be this high in some populations and yet we are not very good at diagnosing it (or looking for it!) sometimes.

The work on combination management of hypertension hasn't been studied in cats but the preferential dilation of afferent renal arterioles with calcium channel blockers has been shown to increase intraglomerular pressure, therefore the addition of an ACEi (which preferentially dilates the efferent arteriole) is likely to be beneficial. There is no reason that this would not be the same in cats. So, even if you dont see massive differences in systemic blood pressure with the ACEi, you are likely to be having benefits on glomerular pressures. Otherwise this may be to the detriment on progression of renal disease.

There is a great review of renal causes of hypertension in Veterinary Clinics of North America Small Animal Practice 41 (2011) 63-89. Which discusses all of this if you are interested.

Andy

Re: hyperthyroidism and azotaemia

Rajat — Tue, 15 Jan 2013 16:11:52 GMT

[quote user="Andrew Kent"]If you consider that around 75% of cats with CRF will be hypertensive[/quote]

Do you have a reference for this Andy?

I suppose one can explain human beings being put on them for something to unique to that species' physiology vis a vis cats...

Re: hyperthyroidism and azotaemia

Kate Richardson — Tue, 15 Jan 2013 13:54:19 GMT

I feel that hypertension is more likely to cause glomerular damage and lead to protein loss if not treated adequately and on a clinical level haven't found increased protein loss in cats treated with amlodipine and clinically I just don't find that ace inhibitors are effective enough in reducing BP. And you have to consider other organs that show end stage hypertensive damage, so I just try to get the best control of BP I can in the simplest way. And I would also prefer to give cats one tablet rather than 2 if at all possible. But as long as we obtain the same end result I guess is the most important thing

Re: hyperthyroidism and azotaemia

Andrew Kent — Tue, 15 Jan 2013 12:33:44 GMT

[quote user="Kate Richardson"]

[quote user="Andrew Kent"]

Equally lots of cats will have a significant improvement in BP/UPC on low doses in which case I maintain that dose.

[/quote]

I personally find ACE inhibitors pretty ineffective in reducing BP. In cats that are neither hypertensive nor proteinuric I am skeptical about the benefits of ACE-inhibitors however some people swear by them. And I have seen lots of cats live for a very long time with renal insufficiency both on medication and not and with or without concurrent problems. The rate of progression does seem to be very variable.

[/quote] I agree that many cats with hypertension may need additional medication to fully control it but many don't. Equally I rarely use calcium channel blockers without and ACEi as logically their preferential action on the afferent arterioles could promote proteinuria in CRF patients.

Re: hyperthyroidism and azotaemia

Kate Richardson — Tue, 15 Jan 2013 11:19:42 GMT

[quote user="Andrew Kent"]

Equally lots of cats will have a significant improvement in BP/UPC on low doses in which case I maintain that dose.

[/quote]

Re: hyperthyroidism and azotaemia

Andrew Kent — Tue, 15 Jan 2013 10:38:23 GMT

[quote user="scatty"]

[quote user="Andrew Kent"]Dear Scatty,

it is not unusual for cats to become azotaemic when you start treating them as their GFR will decrease on treatment, sometimes this improves on its own with time and so if the cat is well I may just check it again in a couple of weeks and see if it is resolving. You could consider reducing the dosing if it is not improving or worsening, I agree that vidalta is probably easier for this as you could consider 10mg EOD and adjust based on your results.

I think a renal diet would be a good idea as long as the cat is not too skinny as they are very protein restricted.

the one thing I would not do is start Benazepril at this stage, ACE inhibitors will also markedly decrease the GFR when they are first started and so you would make the azotaemia worse with these, wait until the figures are a bit more stable and then measure BP and UPC before considering the slow up-titration of an ACEi if indicated. Andy

[/quote]

Also brings me on to another point - do you use ACE inhibitors for many of you CRD cases Andy? It sounds like you are very careful with it by titrating the dose upwards which sounds good! (reducing GFR in a CRD case obviously not being a good idea?!)

[/quote]

If you look at the human guidelines on chronic renal failure then you will see that most people will get put onto an ACEi, but in veterinary medicine we seem to have this idea of all or nothing rather than the slow increase in people. If you consider that around 75% of cats with CRF will be hypertensive there is pretty good reason to use them in the majority of cases but especially if hypertensive or proteinuric.

so yes I probably do use them in the majority of chronic renal failure cases that I treat, but I start at about a quarter of the label doses and increase them over a few months as long as the degree of azotaemia remains stable. Equally lots of cats will have a significant improvement in BP/UPC on low doses in which case I maintain that dose.

of course this approach probably doesn't suit all clients as it requires closer monitoring and more regular visits than some people may like.

Andy

Re: hyperthyroidism and azotaemia

Kate Richardson — Tue, 15 Jan 2013 10:11:05 GMT

Good advice from all.

A few things to add- I agree Vidalta eod is probably the better option for the reasons Andrew mentioned, but in practice felimazole sid can work as well, and is useful if cats won't take whole tablets easily as it can be crushed or they are happier to take a sugar coated pill, and as with all things, some cats tolerate Felimazole better then Vidalta.

I don't use ACE-inhibitors routinely for cats with renal insufficiency unless they have elevated UPC or are possibly if they are hypertensive I might add it in depending on the level of hypertension. Again as Andrew pointed out, they can lead to a temporary increase in azotaemia so it will just confuse the issue in a case like this.

Check and monitor BP regularly if you confirm concurrent renal insufficiency.

Ideally always try to get a urine sample at the onset of treatment for hyperthyroidism so you know what SG is before you start- it may give you a heads up that the cat has subclinical renal disease which is being masked by the hyperT even if there is no azotaemia. As a guide if it is < 1.030 I am strongly suspicious of concurrent CRI, if it is between 1.030 and 1.040 I am mildly suspicious and if >1.040 I am less worried, but when you do your follow up bloods after a month of treatment, check USG as well.

[quote user="scatty"]I have read that cats that are non azotaemic at diagnosis but develop azotaemia during treatment live as long as cats that do not develop azotaemia (whereas if the cat had been azotaemic at the time of presentation this would have been associated with a poorer prognosis). This is encouraging but I'm still not quite sure what action I should take? Surely I can't ignore this?! [/quote]

Unfortunately I think that regardless of when the azotaemia develops, if a cat has concurrent hyperthyroidism and renal disease the prognosis is poorer. Some hyperthyroid cats have mild azotaemia at diagnosis which is not due to renal disease, and the azotaemia resolves when their thyroid is under control. Hence the importance of measuring USG. Azotaemia is meaningless in most cases without a USG. However, with the right balance of medication and monitoring, cats can still do very well for long periods with both diseases especially if any changes to medications are made gradually so as to avoid dramatic changes to GFR.

With regard to performing thyroidectomies in such cases, I don't think it should be complete rule out. If there is great difficulty medicating the cat, and the clinical signs of hyperthoidism are such to be causing reduction in QOL for the cat then I think it has to be considered with a fully informed and understanding owner. It would depend on many factors including what stage of renal disease they had, and preferably after 6 months or so of demonstrating stable renal disease whilst on thyroid medication.

Finally! I was quite excited about y/d initially, but one of my main concerns was the loss of control it would lead to wrt monitoring these cases with owners purchasing the food via the internet and it sounds as though my fears were valid ones. Wouldn't say I wouldn't use it, but less keen.

Re: hyperthyroidism and azotaemia

scatty — Tue, 15 Jan 2013 09:11:06 GMT

By high range , I obviously mean high normal not high high!

Re: hyperthyroidism and azotaemia

scatty — Tue, 15 Jan 2013 09:09:33 GMT

Thank you so much for all your suggestions - will definitely alter the meds and aim to get the reading in high range. I will also start a renal diet. I'll let you know how I get on!

Re: hyperthyroidism and azotaemia

scatty — Tue, 15 Jan 2013 09:08:19 GMT

[quote user="robloxley"]

What is & was urine SG?

[/quote]

Not sure yet - on my to do list!

Re: hyperthyroidism and azotaemia

scatty — Tue, 15 Jan 2013 09:07:44 GMT

[quote user="Andrew Kent"]Dear Scatty,

I think a renal diet would be a good idea as long as the cat is not too skinny as they are very protein restricted.

[/quote]

Re: hyperthyroidism and azotaemia

Anthony Dennison — Mon, 14 Jan 2013 16:52:29 GMT

If I remember rightly, Hills had to change the marketing of Y/D slightly to make sure it was sold as just a food rather than a medication for hyperT4, hence avoiding lengthy delays with things like making it a POM etc

Re: hyperthyroidism and azotaemia

Andrew Kent — Mon, 14 Jan 2013 14:23:30 GMT

And ou don't need a prescription for YD. The term prescription diet is a hills trademark - there are no diets that require a prescription!

Re: hyperthyroidism and azotaemia

Dagmar Steele — Mon, 14 Jan 2013 14:22:27 GMT

+1 for reducing to 2,5mg sid and rechecking after three weeks. Would put on renal diet and try to keep T4 in high normal values. I would not operate on these cats as there's no way back then and all literature I found on this says the same. Re y/d: Only patient I've put on it and eats it is reportedly doing well, owner buying food on the internet, never seen the cat again. No prescription needed, food only sold by vets but that's it...

Re: hyperthyroidism and azotaemia

Andrew Kent — Mon, 14 Jan 2013 14:22:17 GMT

The theory with felimazole is that once daily dosing is not really ideal as the drug is short acting and so those cats have big fluctuation in drug levels which is probably worse for GFR (going up and down) than being steady.

vidalta is a long acting preparation and is low licensed to be given every other day if needed, and the absorption can also be altered depending on whether given with or without food. The drug company showed that even on every other day because it is a slow release formulation that the levels are fairly steady.

so, my preferred strategy for these cats would be to start on 10mg every other day to try to get a balance between T4 and GFR and then increase frequency if needed. Ultimately it may be better to have a T4 at the upper end of the reference interval in order to maximise renal function. Andy

Re: hyperthyroidism and azotaemia

Rob Loxley — Mon, 14 Jan 2013 14:17:35 GMT

What is & was urine SG?

Re: hyperthyroidism and azotaemia

Neil Wheadon — Mon, 14 Jan 2013 14:13:52 GMT

[quote user="Andrew Kent"]you could consider 10mg EOD and adjust based on your results.[/quote]

Can you expand on this please Andrew

It looks like this provides a balance between keeping both diseases at bay.

There was a great article in Vet Times a few months ago, saying that give all cats tablets first for 28 days and if signs of azotaemia, don't operate. It wasn't written what to do afterwards if you do get azotaemia and this looks like a way forward (and easier on the owner/cat.)

Neil

PS In reply to Y/D, don't the owners need a prescription?

Re: hyperthyroidism and azotaemia

Bob Russell — Mon, 14 Jan 2013 14:03:01 GMT

I would be reluctant to consider the y/d route suggested by Hills. We have two patients diagnosed and put onto y/d. No further contact for months because owners started to buy the food on-line.

Y/d has not worked in either case so 'proper' treatment has been delayed by the internet!

Re: hyperthyroidism and azotaemia

Robin Grimmer — Mon, 14 Jan 2013 13:23:36 GMT

+1 for reducing felimazole to 2.5mg sid. I would introduce a renal diet - they are higher in energy due to higher fat content so are meant for putting weight on.

Re: hyperthyroidism and azotaemia

Andrew Kent — Mon, 14 Jan 2013 11:57:02 GMT

Dear Scatty,

I think a renal diet would be a good idea as long as the cat is not too skinny as they are very protein restricted.