creatinine trouble

[DMDcanada]

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Its been a while since i did my renal phsyiology..

I was just wondering the following......if a patient has say, hypercalcemia, and consequently nycturia or polyuria, i understand that this is a result of a decreased ability of the kidney to concentrate the urine... but my question is, wouldnt the creatinine values be elevated?? or not necessarily? the patients creatinine values were normal. why was she uriniating more? was it simply an osmotic diuresis cause by excess calcium???

 

[fang]

Its been a while since i did my renal phsyiology..

I was just wondering the following......if a patient has say, hypercalcemia, and consequently nycturia or polyuria, i understand that this is a result of a decreased ability of the kidney to concentrate the urine... but my question is, wouldnt the creatinine values be elevated?? or not necessarily? the patients creatinine values were normal. why was she uriniating more? was it simply an osmotic diuresis cause by excess calcium???

Cr is a byproduct of muscle breakdown, and is cleared by the kidney in proportion to the GFR (Cr clearance is an estimation of GFR). In hypercalcemia, the mechanism of polyuria is impaired Na rebsorption; GFR is unaffected. If polyuria leads to intravascular volume depletion, the Cr can be elevated from pre-renal ARF.