Does collection method alter urine specific gravity in the cat when using a refractometer?

Re: Does collection method alter urine specific gravity in the cat when using a refractometer?

danielle83 — Wed, 23 Nov 2011 12:06:56 GMT

Hi guys, Thank you very much for your replies. The primary reason I have suggested this optional annual urine screening is to aid early detection of renal dysfunction. USG is the primary focus of the urinalysis, with further tests if warranted base on results, history and clinical signs (necessity for further work up will be determined by a veterinary surgeon). I had not considered to possibility of inaccuracies in results based on collection method until this point was raised by the practice partners then once considered I thought it perfectly feasible. Unless the owners were using a brand new litter tray that day there could be litter and/or cleaning product residue in there which could potentially alter USG. In addition to this there is the potential for contamination from the patient. After this my intrigue has grown and I began researching how collection methods affect results with little success! I do think on the whole the practice partner is supportive of the idea and is just ensuring that we are following the best possible protocol. Also he knows I am at present working through my research module of my advance diploma so thought that it would be good to consider an evidence based approach. Thanks again everyone!

Re: Does collection method alter urine specific gravity in the cat when using a refractometer?

Sal the 1st — Wed, 23 Nov 2011 11:11:12 GMT

[quote user="Danielle Pountain"]Hello my learned peers, I am hoping to introduce routine urine specific gravity analysis in our feline patient in excess of 7 years if age. My proposal suggests same clection via free flow non-absorbable cat litter conducted at home by the client. However a point raised by a practice partner was the possibility if inaccuracy due to collection method and potential artefacts etc. I have searched and searched for published studies on this subject to no avail! Do any if you have experience in this area and perhaps know of any unpublished studies that may have evaluated the effects of collection method on urinalysis results (primarily USG). Thank you to all who have taken the time to read this post :-) Best wishes Danni

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You know the more I think about this the more I think - well, unless the USG is of primary concern in a particular case, wouldnt the concern over inaccuracies in the USG also be a problem in all the other parameters you are testing as well? ( try collecting a fresh dog pee sample off a new concrete path and the ph 8/9 it will raise your eyebrows somewhat but a repeat catheter sample was only ph7) The stick test only highlights areas that may require closer examination or further diagnostics - or is it that you are only monitoring USG?.

I just wondered on how keen the partner is for you to be doing this? - ie are they finding reasons for you not to be doing this? and no I am not trying to put you off its an area that I am really interested in. I picked up two of the diabetics in my previous practice on a routine urine sample provided at an after 8's appointment. ( they were then made a vets appointment ) I do feel that nurses appointments are a lot more valuable than they are given credit for sometimes.

Re: Does collection method alter urine specific gravity in the cat when using a refractometer?

Sal the 1st — Wed, 23 Nov 2011 10:50:38 GMT

[quote user="Juliet Drummond DAVN (med) RVN D32/33"]

you could always centrifuge the sample and do the usg on the supernatant.

one lecture i went to at bsava suggested this for all chemical analysis of urine (dipstick etc)

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Re: Does collection method alter urine specific gravity in the cat when using a refractometer?

Juliet Drummond DAVN (med) RVN D32/33 — Wed, 23 Nov 2011 10:47:39 GMT

you could always centrifuge the sample and do the usg on the supernatant.

one lecture i went to at bsava suggested this for all chemical analysis of urine (dipstick etc)

Re: Does collection method alter urine specific gravity in the cat when using a refractometer?

Vicky RVN — Wed, 23 Nov 2011 09:38:53 GMT

[quote user="Sal the 1st"]

as an aside hibi used to clean katkor so it can be reused (and plenty of places do it) will affect ph no matter how careful you are and how well you have cleaned it.

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That's interesting...if we wanted to collect a sample in house at my last practice we would wash with hibi and autoclave it.

Re: Does collection method alter urine specific gravity in the cat when using a refractometer?

Sal the 1st — Wed, 23 Nov 2011 09:31:33 GMT

well I can tell you that Katkor doesnt and cleaned dry pea gravel doesnt (if it has been pre-washed and is free of grit) but can affect ph unless it has been cleaned many many times, presumably practice partner was concerned about artefacts and evaporation too?

Any other materials used I couldnt vouch for but you could maybe try them out the same way I did. Fresh urine sample test as you would nomally and then use a set amount mixed with your litter material, leave for an hour or a time determined by yourself and then test the sample again, that should give you your answer. TBH unless its the USG that is of primary concern over everything else you are testing for (and our cat was) I have never had this queried before, I think its fair to point out that most owners wont be hanging around the litter tray all day waiting for a sample so it is not very likely they will ever be collecting a sample while its still warm. If it is a sample collected at home just use it as an indication and if the USG is of concern maybe suggest a cysto sample in the clinic. Whatever the substrate it has to be both cat and owner friendly - and lets face it cats are a law unto themselves. I think its commendable if most cat owned can get a urine sample in the first place!

as an aside hibi used to clean katkor so it can be reused (and plenty of places do it) will affect ph no matter how careful you are and how well you have cleaned it.

Re: Does collection method alter urine specific gravity in the cat when using a refractometer?

Nicola Smith — Wed, 23 Nov 2011 09:25:20 GMT

Cant see that it would alter it unless it was inadvertently watered down by water in tray or container. Only thing I would say is that many cats wont toilet indoors if used to going outdoors so may not work for some.