6 y.o DSH cat with hyposthenuria

Re: 6 y.o DSH cat with hyposthenuria

Christopher Saul — Fri, 28 Jan 2011 23:24:14 GMT

Sorry to rabbit on here but I thought I should add that renal imaging is important, particularly before getting to water dep stage. What if this cat has a renal tumour? Could the cat have some persian in its blood line and have polycystic kidney disease? You wouldn't know without imaging.....

Re: 6 y.o DSH cat with hyposthenuria

Christopher Saul — Fri, 28 Jan 2011 23:11:30 GMT

This is a difficult case. All of the differentials that everyone has mentioned are indeed possible (including hyperthyroidism, I have recently seen a case of hyperT4 in a 6 year old cat; though I conceed this is unusual) . Cushing's has been described in nondiabetic cats, and so has diabetes incipidus.

Here's a few musings.......

When I think about these unusual cases I like to remember that 'common things are common'..... If this were my case I would - particularly in view of the limited funds - try and eliminate the slightly less uncommon differentials before persuing the even rarer ones! Aside from the rarity of DI, water deprivation or ADH response tests should only be performed in cases where you have already narrowed the differentials down to psychogenic PD, Central DI, neprhogenic DI. I wouldn't do these where other differentials have yet to be ruled out.

I'd repeat the electrolytes - I'm probhably wrong with this one but can't help wondering if maybe the 'wobbly' episodes are associated with hypokalaemia - if there was some haemolysis with the original sample then this might have masked hypokalaemia. If you do have a severe hypokalaemia then I'd start thinking along the lines of conn's syndrome (hyperaldosteronism) - having said this the normal BP makes this unlikely.

You could help to eliminate hyperthyroidism by doing a Free T4 (eq. dialysis). I'd prob request a bile acid as well if you haven't already done so.... the high urea and lack of liver enzyme elevations makes hepatopathy unlikely but bile acids aren't exactly expensive. .

My next step would be to image the cat - in particular ultrasound of the kidneys and adrenals - together with a full urinalysis by cysto. Kate's suggestion of a trial of amoxy/clav if the culture comes back -ve is prob sensible given the lack of funds.

For elimination of cushing's, I agree with Kate, I'd go for the dex supression test.

[quote user="shanners"]

Does anyone have any experience with a ADH response test, and will it be useful if there is significant medullary washout?

[/quote]

I haven't had much experience with it no, but according to the textbooks medullary washout would indeed significantly affect the ADH response test. As I say though, I'd eliminate the other things first before going down this route.........

These PUPD cases can be a real challenge!!

Hope this helps

Chris

Re: 6 y.o DSH cat with hyposthenuria

shanley barber — Fri, 28 Jan 2011 20:14:50 GMT

[quote user="Kate Richardson"]

However I would also be looking at the kidneys more as well, as suggested above. Has the murmur always been present in the cat? Worth checking blood pressure, especially if htis cat's problems are all related to kidney disease, but flow murmurs also quite common in cats and are benign, but obviously need an echo to determine for certain if the murmur is persistent and no cause such as hypertension found for it.

[/quote]

Thanks, Kate. BP was 120 mmhg, and the murmur was noted when the cat was admitted a year ago.

The polydipsia is profound, he drinks constantly and his urine flooded the prep room! It is truly 'insipid.' I am assuming that, if i do a LDDST and it is normal, then in order to diagnose DI i need to to a water deprivation test; however, this is contraindicated by the high urea. The owner said that he seems to get 'wobbly' if he doesn't get enough water. Looking at his Na, I am assuming that this is the cause, another reason NOT to to the deprivation test.

Does anyone have any experience with a ADH response test, and will it be useful if there is significant medullary washout?

Thank you!

Re: 6 y.o DSH cat with hyposthenuria

Anonymous — Fri, 28 Jan 2011 14:09:36 GMT

[quote user="Kate Richardson"]

I would think hyperthyroidism would be fairly unlikely in a 6 year old cat, and to be honest I haven't seen a usg as low as that secondary to hyperthyroidism, usually 1.020-1.030 if it is due to hyperT only (ie no concurrent renal insufficiency)

[/quote]

Don't disagree with you here, just have an irritation with the reporting of results like T4 as 'normal' in general.

Thanks for the info on Cushing's in cats - very interesting.

If the cat is more or less clinically well (other than PUPD), and the diarrhoea is unrelated, and has consistently isothenuric urine (pretty cheap to test), then I'm struggling for likely differentials other than Cushings, DI or psychogenic polydipsia - none of which are particularly common in cats...

Re: 6 y.o DSH cat with hyposthenuria

Kate Richardson — Fri, 28 Jan 2011 13:46:10 GMT

Have just dug out some notes I have on hyperA in cats- no sex/breed predisopsition, average age 10years old, . Historically PUPD (90%), polyphagia (70%), weight loss (35%), lethargy/weakness (30%).

Clinically clinical signs- abdominal enlargement, alopecia, thin/fragile skin, muscle wasting, infections, rough/dry coat, hepatomegaly, Can have concurrent pancreatitis.Hyperglycaemia is present in 90% of cases, but only 80% have overt DM. Increased cholesterol and ALT present in 50% of cases, AST and ALKP elevations next most common finding, but can be normal Cats do not possess a steroid induced iso-enzyme of ALKP, so if ALKP is elevated, it usually ocurs secondary to DM. Lymphopaenia is most common haematology finding.

Most cats with hyperA are PDH. To test- a urine cortisol:creatinine ratio can rule it out if within normal rangs, but a high one doesn't confirm it. You need to do a dexamethasone suppression test- books sometimes call it a low dose one, but you should actually use the the high dose dex (0.1mg /kg iv) and measure cortisol at 0,4 & 8 hours

Hope that helps?

Re: 6 y.o DSH cat with hyposthenuria

Anonymous — Fri, 28 Jan 2011 09:28:03 GMT

Might be worth repeating a few more SG readings (making sure refractometer calibrated accurately etc). If was consistently isothenuric then structural kidney disease would be high on list of differentials, if was consistently hyposthenuric, i.e. <1.006, then kidney is actively diluting glomerular filtrate and I would have thought structural kidney disease like occult pyelonephritis to be rather unlikely and not good value for the client's limited budget to be investigating?

I don't think normal liver enzymes rules out Cushing's even in a dog (from memory, as many as 20% won't have elevated ALKP), so I guess it remains somewhere on the differential list. One person's 'normal' T4 is another person's 'possible hyperT4', so I wouldn't entirely rule that out either (although if T4<30 then is pretty unlikely); I sometimes see cases (not like this one) where clinical notes have recorded 'T4 normal' in a cat with signs of hyperthyroidism, that is systemically unwell, and when checked the actual result is 60 (top of reference interval)...

Re: 6 y.o DSH cat with hyposthenuria

Kate Richardson — Fri, 28 Jan 2011 09:08:44 GMT

How marked is the pupd? Is it possible that there is some medullary wash out? Chris, you may be able to comment on that.

I would also add that even if the cysto cultures negative, I would probably still opt for a 2 weeks course of clav, just to be as certain as I could be there wasn't an occult pyelonephritis, but that's just what I do.

Re: 6 y.o DSH cat with hyposthenuria

shanley barber — Thu, 27 Jan 2011 21:21:43 GMT

Thanks, Chris.

Yes, Ca was included, and was normal (2.38) and no abnormalities on the haematology.

Shanley

Re: 6 y.o DSH cat with hyposthenuria

Christopher Saul — Thu, 27 Jan 2011 19:54:23 GMT

[quote user="shanners"]I understand that, as a rule, hyposthenuria means that the kidneys are functioning normally, and we are probably looking at some form of DI, likely nephrogenic[/quote]

Not entirely true.... If you have any degree of azotaemia (as you have, albeit very mild), in the presence of inappropriately dilute urine, then you have demonstrated imparied renal function, though not necessarily structural or primary renal disease. Diabetes incipidus is as you say a possibility, though very uncommon. I take it your blood pannel included calcium? Any haemogram changes?

I agree an inactive sediment makes pyelonephritis unlikely, but it does not completely eliminate it I'm afraid... With very dilute urine the cells can lyse in transit.

I would be inclined to image this cat - ultrasound of kidneys would be my next step. Whilst doing this I would obtain a cysto urine sample for culture and sens and also cytology ( you need a formalin-fixed sample for this)

Sorry for the brief reply, just logged on for a moment and in a hurry! I'll think it over for you...

Chris