Thursday, December 13, 2012

Decline in Feline Urine Specific Gravity Not a Complete Picture Nor Indicates Serious Decline in Renal Function

Good news about Myrna-the MSU called and said her glomerular filtration rate test-or the actual iohexol test-shows she does NOT have renal disease or any decline in renal function. There is a 12% decline from a normal cat but she's well within in normal range reference. Believe decline due to heart meds-lasix, aspirin, enalapril. But she's functioning just fine. 
The tests she had last week at MSU showed that there was potentially no renal disease but the GFR would confirm that.  They did suggest that between her heart meds that affects the amount of water she drinks (which we knew about) and the dietary SO we fed her which also promoted drinking a  lot of water, these would contribute, of course, to frequent urination. 
MSU had suggested we stop feeding her dietary SO because it promotes drinking through an increase in sodium and other additives.  The high level of sodium is not good for kidneys especially if there is a disease or a potential for a disease (and such can be the case with HCM cats due to heart health and heart meds.) We have seen a decline this past week in frequent drinking/urination (previously going about every 2 hrs) since we stopped feeding her SO.  We do need to make sure she still drinks enough.
If your pet drinks/urinates too often, even if on meds, and you are worried about potential renal disease, you need to get not just a CBC/chem panel but a GFR. GFR shows true renal function. The CBC/chem panel only shows a decline in kidney values of BUN, creatinine, etc. once kidneys have reached around 70% decline in function.  So, you could potentially have a good CBC/Chem panel with a high level of BUN and creatinine but a low GFR readout.  The GFR low readout would indicate a renal disease or lack of function while the CBC/Chem panel could be misleading.
Myrna Loy ready for Christmas
The MSU report states the normal reference range is 1.15-2.73 mL/min/kg-each ml of fluid moving through the glomerular in a minute per kg weight of cat-I believe that's how it's measured.  Her reference was 1.700 mL/min/kg. Normal cat's rate is 1.94 mL/min/kg. 

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