?Diabetes Insipidus

Re: ?Diabetes Insipidus

grumpyoldman — Mon, 03 Mar 2014 00:15:16 GMT

if your samples are still at the lab you could ask them to do a pre and post 17 hydroxyprogesterone ACTH stim test ,which picks up the odd atypical cushingoid, we find about half the cushingoid looking dogs are actually positive when tested with 17OH , also lots of labs are over cautious and regard anything that does not go over 660 as negative ,where as Hertage at Cambridge regards anything over 500 post stim as positive

paradoxically these also respond to DDAVP which is why DI responsive dogs happen on inconclusive ACTH tested polydypsic's .

If the moneys running out you maybe able to talk them into a 10 day treatment trial ?.

that is our approach sometimes I hope it helps

Re: ?Diabetes Insipidus

Christopher Saul — Sun, 02 Mar 2014 23:22:37 GMT

Yes I would agree with everything that others have said so far, especially that primary DI is incredibly rare... though being completely pedantic, many causes of PU/PD could in fact be classified as a diabetes insipidus - albeit a secondary, nephrogenic DI.

PUPD can be classified as follows:

*Primary central DI (this is what most people mean when we refer to DI) - rare and doesn't fit with the signalment

*Secondary/acquired central DI (head trauma, brain tumour occupying the neurohypophysis, idiopathic) - uncommon but less rare than primary CDI or primary NDI, so not impossible

*Primary nephrogenic DI - like primary central DI, incredibly rare and doesn't fit with the signalment

*Secondary nephrogenic DI - (meaning there is something interfering with the kidney's ability to respond to ADH) - very common. Hypercalcaemia, cushing's, pyelonephritis, pyometra, addison's, conn's, hypokalaemia, CKD and so on

*Osmotic diuresis - Diabetes mellitus, renal glucosuria, CKD has some degree of osmotic diuresis involved also.

*Primary polydipsia - psychogenic, liver failure, hyperthyroidism

.....So, what to think about this dog?

Well, the first thing I would suggest a urine sample via cysto for culture&sensitivity, cytology and protein : creatinine ratio. I think it highly important to rule out pyelonephritis. Any signs if renal pelvic dilation on ultrasound?? If so could get a urine sample from the renal pelvis under ultrasound guidance.

I know urea and creatinine were normal but where were they within the reference range? if the urea and creat are high in the reference range and urinary protein creatinine ratio is high (maybe high BP too) then this might imply nonazotaemic CKD

I would do blood pressure and electrolytes - pheochromocytoma and hyperaldsteronism are hardly common - rare in fact - but can cause PU/PD. Normal BP doesn't rule it out either, but worth doing?

As Thomas has already suggested, I would do a urinary cortisol : creatinine ratio ON A FREE CATCH SAMPLE TAKEN AT HOME - so the dog is not stressed when the sample is taken. If cortisol :creat is low then eliminates cushing's but tells you nowt if ratio high

where within the reference range was calcium? you could run an ionised calcium to eliminate hypercalcaemia.

ONLY when you have comfortably eliminated the 'secondary/aquired nephrogenic DI' group and osmotic group of causes (see above) would you then look to central DI (as explained above this dog will be secondary rather than primary CDI) as your cause. Any hx of head trauma? an MRI would be indicated at that stage to look for brain tumours etc

if owners cannot afford MRI, and if you have eliminated neprogenic causes, could consider trial DDAVP

Just a few thoughts...

hope this helps

Chris

Re: ?Diabetes Insipidus

Rob Loxley — Thu, 20 Feb 2014 18:53:53 GMT

[quote user="Charlotte Marshall"]Yeah normal response on ACTH stim and LDDS[/quote]

ACTH stimulation has a fairly high false negative rate: the test will miss approx 15-50% of true cases
LDDST performs better but is not perfect even if you do it perfectly; in particular getting the dex s/c rather than IV won't help the false negative rate (I only mention as I've heard it happens)

What's the current feeling on measuring 17-(OH)P?

[quote user="Charlotte Marshall"]no real functional impairment according to the BAS[/quote]

How well the BAS test tells you this is another thread entirely!

[quote user="Charlotte Marshall"] I have told her to let her drink for now[/quote]

Is this not a long-term option?

Re: ?Diabetes Insipidus

Charlotte Marshall — Wed, 19 Feb 2014 22:30:38 GMT

Yeah normal response on ACTH stim and LDDS. Urine ratio might be a good idea thanks folks. I am afraid our ultrasound machine and my skills are not up to finding adrenals (unless it was really big!) though I did find them on the CPD course :)

Re: ?Diabetes Insipidus

Louise Buckley — Wed, 19 Feb 2014 19:54:56 GMT

Couple of random possibilities:

Atypical leptospirosis?

Being fed a raw diet that is rich in gullet? Has a T4 been carried out?

Re: ?Diabetes Insipidus

Thomas Johnson — Wed, 19 Feb 2014 18:37:59 GMT

[quote user="Robin Grimmer"]

I agree with Martin, true DI is incredibly rare. Psychogenic PD is unlikely in this age dog. Cushings is the great 'pretender'. Adrenal dependent HAC in particular can often have normal acth and ldds tests. An ultrasound of the adrenals would be useful.

[/quote]

It might also be worth doing a urine cortisol:creatinine ratio, a negative result will rule out Cushings, a positive result doesn't tell you very much unfortunately.

Re: ?Diabetes Insipidus

Robin Grimmer — Wed, 19 Feb 2014 17:45:13 GMT

Re: ?Diabetes Insipidus

Martin Atkinson — Wed, 19 Feb 2014 17:07:28 GMT

True DI is incredibly rare and there is likely another cause maybe psycogenic. I would still wonder about HAC with your liver enzymes and would want to be certain the LDDS test was performed properly. You say the tests were negative by that do you mean normal response?

I have an HAC dog with classical symptoms that never read the textbook on cortisol levels and the ACTH stim test which was equivocal and the LDDS test was only just diagnostic but it responded well to Synacthen and deteriorated when it came off because its cortisol was getting low, but improved again when re-started when its liver enzymes and cortisol started to rise again (albeit still in normal range)!

I would still say a missed HAC is more likely than DI but in answer to the question, if nothing else if DDAVP controls the symptoms it is not diagnostic of DI but it buys you a bit more time and a happier client.

I also inherited a case treated by another vet for DI with desmopressin and it controlled the symptoms but eventually it showed progressive neurological symptoms and was PTS with a suspected brain tumour. Whether this was causing a psycogenic PD or it was truly affecting its pituitary gland we will never know.

Re: ?Diabetes Insipidus

Charlotte Marshall — Wed, 19 Feb 2014 15:32:55 GMT

Calcium level was normal. I thought that the textbook implied if you got a very large reduction in polydipsia that was confirmatory. It said that if it was psychogenic the decrease would only be about 30% rather than 50 - 80%.

Re: ?Diabetes Insipidus

Miriam Lodewyks — Mon, 17 Feb 2014 21:11:16 GMT

And yes, I'd try DDAVP. Though it doesn't really confirm any diagnoses.

Re: ?Diabetes Insipidus

Miriam Lodewyks — Mon, 17 Feb 2014 21:10:08 GMT

Calcium levels?