hyperthyroid surgery

Re: hyperthyroid surgery

Simon Neuhoff — Fri, 21 Oct 2011 19:00:57 GMT

[quote user="David Mills"]

Interestingly, Edinburgh have the hospitalisation period down to a week with radioactive I as long as cat stays indoors for a period after and all litter's disposed of in clinical waste. Think RVC are not far behind on this. The future beckons...

[/quote]

That sounds good - hopefully will also have the effect of reducing the waiting period too. Given the dramatically better survival times I would like to send more - well any! cats for this.

Re: hyperthyroid surgery

David Mills — Fri, 21 Oct 2011 17:11:51 GMT

Re: hyperthyroid surgery

Amanda Nicholls — Fri, 21 Oct 2011 14:36:01 GMT

I always push for I 131 as it is what I would use for my cats, however, I hardly ever get anyone to go for it. My second choice would be thyroidectomy, stablilised for a couple of months if possible but if owner can't/won't pill I wouldn't hospitalise for longer than 24 hours pre op. I like to have them in the night before on maintenance fluids +/-sedatives to reduce the risk of GA. Not had any complications so far....

Re: hyperthyroid surgery

Simon Neuhoff — Thu, 20 Oct 2011 09:12:59 GMT

As I've said before I have no evidence whatsoever that "premedicating" for 5 days with Vidalta makes any difference - it may well be a "fudge" - but you can create euthyroidism in just 10 days with Vidalta. The data sheet says that TT4 may decrease to euthryoid "shortly after treatment initiation". I have not measured T4 in a cat after 5 days treatment - but I will next time the situation arises out of interest. It is something we do very infrequently so don't hold your breath. To me it seems better than doing nothing but I freely admit this is based on gut instinct and no evidence. If I can find evidence either way I will adapt accordingly. At the very least I think this approach might be somewhat helpful and it does no harm - we don't charge the clients hospitalisation rates for this "boarding" period.

Re renal disease and T4 - I've always understood that the artificially increased perfusion simply raised GFR and masked renal disease - it does not have a protective effect and I also have understood that the high blood flow and increased blood pressure through the kidneys ultimately accelerates renal damage - one of the reasons hyperthryoidism should be controlled. HYPOthyroidism created iatrogenically whether through medication or surgery can have a negative effect on survival rates when associated with azotaemia -again tying back in to the stabilisation phase prior to surgery and affecting your treatment choice. When the animal is euthryoid and not azotaemic then as far as I understand it the renal function should not be affected - or in any case I have not read anything to suggest that.

Re: hyperthyroid surgery

Julian Earl — Wed, 19 Oct 2011 22:55:00 GMT

[quote user="Simon Neuhoff"]

[quote user="Julian Earl"]

[quote user="Simon Neuhoff"]

If you look at papers on thyroidectomy there is general agreement that establishing control before surgery is beneficial. As to whether 5 days of treatment is any better than none I have absolutely no idea. There are no studies that I am aware of that would support that approach but I know of a few vets who do do it - one is a certicate holder. (Note this is in those specific cases where the cleitn cannot medicate the cat).

[/quote]

How and why?

[/quote]

Not sure I understand the question - how - tablets! Why - to reduce anaesthetic risks. Or is that not what you were asking?

[/quote]

[quote user="Simon Neuhoff"]

[quote user="robloxley"]

[quote user="Simon Neuhoff"]If it is 6 months post achieiving euthyroidism then I think this is a "new"problem - they probably did have early renal disease before the thyroidectomy and it has simply progreessed in the natural way. I don't see that this will be affected in any way by how you treat them.[/quote]

When monitoring medically managed cases we will monitor renal parameters as well as T4 and in some cases have seen marked deterioration with improvement in T4, due to unmasking of occult renal disease, to the point of backing off on the thyroid medication dose; if doing surgery without stabalisation what do you do if the kidneys 'decompensate'?

[/quote]

Agreed - one of the reasons that we try to stabilise them prior to surgery even when the owner wants surgery from the outset.

...The point I was trying to make above though is that if the elevated GFR in a thyroid cat is "masking" renal disease then this should be "unmasked" as euthyroidism occurs - within a few weeks at the most I would have thought. Those that Julian mentions that become azotaemic 6 months or more later may have had pre clinical renal issues which have now progressed in the usual fashion - but would have done so irrepsective of how the euthyroidism was achieved. Provided the cat is not hypothryoid then I don't think the treatment option would influence the renal issues.

[/quote]

The how and why were asked to challenge how and why a few days of medical therapy might improve the anaesthetic risk; my understanding of medicating is to facilitate the monitoring for underlying renal disease which, as I suggested before could take a long time to manifest itself.

I am not so sure at all that six months would be too long for renal disease to become apparent - it could easily be that there is, say, twenty per cent loss of nephrons for whatever reason but that the reduced renal perfusion following treatment then accelerates the pathology, ergo, six months before enough pathology is present to cause clinical renal disease. True, the renal disease may well have manifested eventually, but who knows, maybe a year or two years or more?

In other words, premedication for surgery should be for weeks and months not days; reducing the T4 level may well take only a few days but it is not the T4 that directly increases an anaesthetic risk, it is the BP, the cardiac effects, and the metabolic rate. None of these are altered by the tablets within a few days, and the former two not necessarily affected at all. Having said that, I would repeat my comment that so far I have not encountered any anaesthetic emergencies during a thyroidectomy anyway, with or without premedication, so I await proof that short-term premedication is of any benefit at all.

The only benefit of medication that I can see is that, in the event of renal disease subsequently developing, treatment can obviously be reduced or even stopped, but, of course, we can't put the thyroids back in (although we could supplement with tablets which I have mooted before on another thread). As long as bloods are normal, and there is no current evidence of renal disease (in which case I would go for medical rather than surgical therapy), I advise surgery as long as the owners are aware of the risk for renal disease to develop later. I regard renal disease as very treatable now if not curable. However, if the owners would rather use tablets, then so be it, but personally I prefer to solve the problem once and for all by removing the gland(s).

Re: hyperthyroid surgery

David Mills — Wed, 19 Oct 2011 21:58:53 GMT

[quote user="robloxley"]

if doing surgery without stabalisation what do you do if the kidneys 'decompensate'?

[/quote]

I think I'd rather have a cat with CRF than uncontrolled hypert4, generally, but it depends on the figures. It would have decompensated on medication; and its heart would still have been profoundly affected if you 'back off' the meds. Cats cope far better and last longer with CRF than hypert4.

[quote user="robloxley"]

If some people are giving beta-blockers to unstable hyperthyroid cats pre-surgery there must be some cardiovascular rationale, and maybe the same rationale is behind achieving euthyroid status pre-surgery?

[/quote]

Hmm not sure. beta blockers are designed to improve diastolic function, which GA will do, incidentally. And there are far more effective IV preparations to give if worried about/during GA - beta blockers are difficult to give in cats, and it can be very hazardous to stop them suddenly (beta receptor downregulation) or start them at too high a dose.

My original post was whether people had seen problems with the approach we're trialling. Aware of the theoretical problems. But it's interesting that we know the theory of why they should be stabilised but whether this actually translates into clinical significance - and I see the 5-day stabilisation as a fudge.

Re: hyperthyroid surgery

David Mills — Wed, 19 Oct 2011 21:58:53 GMT

[quote user="robloxley"]

if doing surgery without stabalisation what do you do if the kidneys 'decompensate'?

[/quote]

[quote user="robloxley"]

[/quote]

Re: hyperthyroid surgery

Charlotte Marshall — Wed, 19 Oct 2011 20:56:36 GMT

[quote user="Martin Atkinson"]Conspiracy theory: the incidence of feline hyperthyroidism in the UK increased after the Chernobyl disaster - maybe the distribution of disease is related to fallout from the cloud. The incidence of hyperthyroidism varies hugely around the world with lower incidence in those countries with no nuclear industry or are not neighbours to countries that do.[/quote]

The area where she saw hardly any cases was in Cumbria! Not really that far from Sellafield either. However there may have been an element of animals not being presented given the area.

I wondered if levels of iodine in the water or soil could be relevant.

Re: hyperthyroid surgery

Simon Neuhoff — Wed, 19 Oct 2011 19:23:58 GMT

[quote user="robloxley"]

[/quote]

Agreed - one of the reasons that we try to stabilise them prior to surgery even when the owner wants surgery from the outset. Another is the increase in liver values we often see in thyroid cats - if it is due to the hyperthryoidism they should drop in concert with the T4 levels. If they don't then there may be a concurrent hepatopathy - making them less than ideal surgical patients.

The point I was trying to make above though is that if the elevated GFR in a thyroid cat is "masking" renal disease then this should be "unmasked" as euthyroidism occurs - within a few weeks at the most I would have thought. Those that Julian mentions that become azotaemic 6 months or more later may have had pre clinical renal issues which have now progressed in the usual fashion - but would have done so irrepsective of how the euthyroidism was achieved. Provided the cat is not hypothryoid then I don't think the treatment option would influence the renal issues.

I don't know anything about how beta blockers are best used in these cases (we don't use them for pre treatment) but certainly I think your typical tachycardic, hypertensive untreated thyroid cat is a sub optimal anaesthetic candidate.

Re: hyperthyroid surgery

Rob Loxley — Wed, 19 Oct 2011 18:39:11 GMT

Re: hyperthyroid surgery

Simon Neuhoff — Wed, 19 Oct 2011 17:53:36 GMT

[quote user="Julian Earl"]

[quote user="Simon Neuhoff"]

[/quote]

How and why?

[/quote]

Not sure I understand the question - how - tablets! Why - to reduce anaesthetic risks. Or is that not what you were asking?

Re: hyperthyroid surgery

Julian Earl — Wed, 19 Oct 2011 17:12:49 GMT

[quote user="Simon Neuhoff"]

[/quote]

How and why?

Re: hyperthyroid surgery

Simon Neuhoff — Wed, 19 Oct 2011 16:03:20 GMT

[quote user="Julian Earl"]

[Second point: how many cats treated by bilateral thyroidectomy have gone on to show either persistent symtoms or a recurrence of signs? I am highly sceptical of the (Intervet?) claims that one in three cats have intrathoracic thyroid tissue:

1. What proportion of cats do have this tissue in other independent studies?

b) If they do have some, how much do they have?

(iii) If they have a significant amount of tissue, how physiologically active is it?

4. If it is physiologically active, will it automatically become hyperactive tissue?

(e) If it does become hyperactive tissue, how long is it likely to take to do so following the surgical treatment of the original glands?

(vi) Following on from (e), what are the chances of it being within the lifetime of this already presumably not-young cat?

7. If it does become hyperactive within the lifetime of the cat, how long is it likely to take before it affects the welfare of the cat to a degree that it requires further therapy?

[/quote]

From:

Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands. E.C.Naan@vet.uu.nl

5 of 101 cats had recurrence of hyperthryroidism following bilateral thyroidecomty - of these 4 had ectopic thyroid tissue. The time taken for recurrence rnaged from 3 months to 59 months.

Re: hyperthyroid surgery

Simon Neuhoff — Wed, 19 Oct 2011 15:19:14 GMT

[quote user="David Mills"]

[quote user="Julian Earl"]

I don't quite understand the point of just treating them for a few days pre-operatively. The occurrence of renal disease can be months after the treatment has started - I know this because we were operating on all cats with the signs in the mid-eighties and a few did develop renal disease six months or so later; no-one made the connection immediately. So what is the point of medicating, even for weeks for that matter? Are there studies to show the benefits on anaesthetic risk, or on renal disease or other morbidity? I cannot recall a hyperthyroid cat having an anaesthetic -related complication when not medicated first so remain to be convinced that it is essential.

[/quote]

This is what we've found, and our ethos. What's the point in messing around with meds for a few days or non-compliant weeks when you can operate on them in 30-60m and have permanent resolution? Admittedly, we are a London charity clinic so cost is high up on the list i.e. its cheaper for us to operate than medicate. And we do one-sided. I don't think that's negligent any more than, for instance, cruciate sx where you leave the 'normal' knee alone - as for the 70-80% I'm skeptical about this.

Likewise, I think the 33% intrathoracic tissue argument is a complete myth.

[/quote]

Dutch study found ectopic tissue in 9 out of 101 cats assessed with scintigraphy.

US study (Cornell University) said over 80% are bilateral at time of presentation. In my view a unilateral thyroidecomty is not at all comparable to doing a "unilateraly" cruciate - doing a bilateral cricuiate - operating on the normal knee before the ligament ruptures would be a prohylactic procedure and it would render the dog unable to walk if done simultaneously not to mention in great pain. NOT the same thing as operating on an animal that has bilateral disease at the time of presentation. If you are not confident in your operative technique and "stage" the procedure, and you explain this to the client, then that is your choice. "Staging" the procedure would not be the same as waiting for the cat to become hyperthyroid again in my opnion but rather akin to staging a bilateral mammary tumour removal - ie a deliberately planned two stage operation.

Edit - note by "you" I mean the operating veterinarian - not wanting to cast aspersions as it were!

Re: hyperthyroid surgery

Simon Neuhoff — Wed, 19 Oct 2011 15:04:39 GMT

[quote user="Julian Earl"]

[quote user="Charlotte Marshall"]

We do quite a few thyroidectomies and normally stage the procedure if both sides are enlarged. If the owners can't medicate we have had them in for a few days to pill beforehand.

I also find there can be quite a gap between surgeries and we have quite a few cats who do not have the other side done either they stay on medical mangement the second time or the cat succumbs to some other problem before they become hyperthyroid again.

Interestingly a friend of mine who has worked in different areas of the country said she was aware of a big difference in incidence of hyperthyroidism. She worked in one palce where they hardly saw any at all and others where it was very common. Has anyone else found this? I have been in the same place for years and I would say it is probably the most common endocrine problem I see.

[/quote]

These are older cats - many of them will develop renal disease regardless of anything else going on. How do you determine whether it is linked to the thyroid issue? If it is 6 months post achieiving euthyroidism then I think this is a "new"problem - they probably did have early renal disease before the thyroidectomy and it has simply progreessed in the natural way. I don't see that this will be affected in any way by how you treat them.

If you look at papers on thyroidectomy there is general agreement that establishing control before surgery is beneficial. As to whether 5 days of treatment is any better than none I have absolutely no idea. There are no studies that I am aware of that would support that approach but I know of a few vets who do do it - one is a certicate holder. (Note this is in those specific cases where the cleitn cannot medicate the cat).

Re: hyperthyroid surgery

David Mills — Wed, 19 Oct 2011 13:34:49 GMT

[quote user="Julian Earl"]

[/quote]

Likewise, I think the 33% intrathoracic tissue argument is a complete myth.

Re: hyperthyroid surgery

Julian Earl — Wed, 19 Oct 2011 13:18:49 GMT

[quote user="Charlotte Marshall"]

We do quite a few thyroidectomies and normally stage the procedure if both sides are enlarged. If the owners can't medicate we have had them in for a few days to pill beforehand.

[/quote]

Second point: how many cats treated by bilateral thyroidectomy have gone on to show either persistent symtoms or a recurrence of signs? I am highly sceptical of the (Intervet?) claims that one in three cats have intrathoracic thyroid tissue:

1. What proportion of cats do have this tissue in other independent studies?

b) If they do have some, how much do they have?

(iii) If they have a significant amount of tissue, how physiologically active is it?

4. If it is physiologically active, will it automatically become hyperactive tissue?

(e) If it does become hyperactive tissue, how long is it likely to take to do so following the surgical treatment of the original glands?

(vi) Following on from (e), what are the chances of it being within the lifetime of this already presumably not-young cat?

7. If it does become hyperactive within the lifetime of the cat, how long is it likely to take before it affects the welfare of the cat to a degree that it requires further therapy?

Re: hyperthyroid surgery

Kate Richardson — Wed, 19 Oct 2011 11:52:03 GMT

[quote user="Jillian Hall"]

[quote user="Toby Birch"]Hills have launched Y/D in the US.[/quote]

Is there anybody out there in the know about this. I've seen the adverts on american websites and loked at the Hills site (it works on the basis of having very very low levels of Iodine so the body doesnt have enough to physically manafacture thyroid hormone.)

But what I don't see is any evidence of whether it works or not. If it did I expect it will make a big difference ot a lot of clients and their cats.

[/quote]

At the ESFM congress this year, there was a presentation on y/d and the evidence presented was very convincing, return to euthyroidism in about the same amount of time as with medication, so very promising. I can have a look through my notes and see if I have a hard copy of the research so far, otherwise you could ring Hill's and I am sure they would be able to send you something.

Re: hyperthyroid surgery

Hannah Wynne Richards — Wed, 19 Oct 2011 11:17:52 GMT

Possibly difference in incidence in cats PRESENTED to veterinary surgeons Some areas owners more likely to think it's "old age " and so never present

I've now educated my clients, so have a lot of "old creakys ) on the books When I bought the practice I had a lot of conversations:

Me "This cat is too thin, I ought to investigate it "

Owner "He's old "

Me "That doesn't mean I can't help him "

Wynne

Re: hyperthyroid surgery

Jillian Hall — Wed, 19 Oct 2011 10:49:45 GMT

[quote user="Toby Birch"]Hills have launched Y/D in the US.[/quote]

But what I don't see is any evidence of whether it works or not. If it did I expect it will make a big difference ot a lot of clients and their cats.

Re: hyperthyroid surgery

Martin Atkinson — Wed, 19 Oct 2011 10:23:08 GMT

[quote user="Charlotte Marshall"]

[/quote]

Conspiracy theory: the incidence of feline hyperthyroidism in the UK increased after the Chernobyl disaster - maybe the distribution of disease is related to fallout from the cloud. The incidence of hyperthyroidism varies hugely around the world with lower incidence in those countries with no nuclear industry or are not neighbours to countries that do. The only apparent epidemiological predisposing factor is feeding fish or fish flavoured cat food (that is a fact not a conspiracy theory) do countries that have low incidence source their fish from less contaminated water? It will be interesting to see if the incidence of feline hyperthyroidism increases in Japan post Fukushima, the incidence of thyroid cancer is expected to increase in the human population. I'll keep you posted on my daughter who was there at the time, ironically her younger sister who has never been near Japan has Graves disease! The incidence of human thyroid cancer did increase in the Ukraine post Chernobyl but interestingly that of other forms of cancer did not which was rather surprising.

Re: hyperthyroid surgery

Charlotte Marshall — Tue, 18 Oct 2011 22:38:31 GMT

We do quite a few thyroidectomies and normally stage the procedure if both sides are enlarged. If the owners can't medicate we have had them in for a few days to pill beforehand.

Re: hyperthyroid surgery

Simon Neuhoff — Tue, 18 Oct 2011 17:26:18 GMT

[quote user="Rob Davis"]

[quote user="Simon Neuhoff"]Given that 70-80% of cats will experience bilateral disease I think a unilateral thryoidectomy is plain wrong - it borders on ripping the client off. .[/quote]

I disagree - as long as the owner is informed of the risk of the disease occuring in the remaining thryoid gland in due course, I don't see a problem with this.They usually seem to take around 18 months to develop the problem on the other side.

[quote user="Simon Neuhoff"]It is not safer to do a staged procedure either - either you preserve the parathyroids or you don't.[/quote]

I disagree with this too - I think most parathyroid problems are because of disruption of blood supply rather than complete excision, and the blood supply is usually re-established within a relatively short period post-op, hence it is often only necessary to supplement vitamin D / Calcium temporarily.

Having said that, if both thyroids look enlarged then I will perform bilateral surgery rather than staging the procedures, but I usually hospitalise for a couple of days afterwards to monitor Calcium levels. Unilateral thyroidectomies I send home on the same day, so once hospitalisation and blood test costs are added, bilateral surgery costs almost exactly double unilateral surgery, so even if you do need to operate on the other side in the future, it can hardly been described as ripping the client off.

[/quote] Shrug - I suspect your charging structures are quite different to ours then. Certainly three days in hospital and three calcium tests does not work out anywhere near half the cost at our clinic. Are you factoring in the costs of repeat diagnosis and stabilisation when it recurs? Also bear in mind the cat is now 18 months older. To me this is doing half the job. Re the safety aspect - if the damage is temporary then there would be an advantage. (I suspect this is only occasionally a factor though.

Re: hyperthyroid surgery

Kate Richardson — Tue, 18 Oct 2011 16:03:44 GMT

[quote user="Rob Davis"]

[quote user="Simon Neuhoff"]Given that 70-80% of cats will experience bilateral disease I think a unilateral thryoidectomy is plain wrong - it borders on ripping the client off. .[/quote]

[/quote]

Absolutely agree with you Rob

Re: hyperthyroid surgery

Kate Richardson — Tue, 18 Oct 2011 16:02:04 GMT

Going back to OP, unless the cat is absolutely impossible to medicate, then I will always try to stabilise medically prior to surgery. And I always get the owners to try to medicate even if they really, really, REALLY don't think they will be able to, they quite often come back and say that they managed to find something the cat just couldn't resist and these cats are usually polyphagic. I also show them different techniques of directly medicating, as many clients think they can't, but when shown, actually find they can. My own cat was a nightmare initially, but now he practically opens his mouth for me! I think assessment of renal function is very important to establish before and after they achieve euthyroidism.

However, if the risks were fully explained to the owner, then I have and would still perform a thyroidectomy without prior stabilisation if the circumstances meant that it was the only option. But I wouldn't do it as a routine.

[quote user="Martin Atkinson"]I have done dozens of thyroidectomies and hardly ever feel I've reliably identified the parathyroids (maybe its my eyesight but can anyone honestly say they can identify and dissect them reliably)?, yet I've only had one become permenantly iatrogenic hypoparathyroid[/quote]

I'm glad it's not just me then! And they look so obvious in all the diagrams, sometimes they are even bright blue in colour! But the modified intra-capsular technique does seem to be the best technique.

Personally I like Vidalta, compliance is better due to it being once daily plus does seem to be more tasteless than Felimazole, and I have had a few serious adverse effects with Felimazole, plus it is bitter. Personally I have had good results with Vidalta as well. I also do few thyroidectomies now, and tend to manage medically, that said, if the cat is young then I consider thyroidectomy early, and never rule it out as an option for treatment.