Need explanation of Creatinine clearance

[missmollie, ADN, BSN, RN]

I have read my book, I have have searched wikipedia, google, and I am confused about creatinine clearance. Here is what I know:

-Normal serum creatinine is 0.6-1.3 mg/dL

-Creatinine is a by product of muscles

-It is the "gold standard" test for kidney function because only renal disease increases creatinine (happens after 50% of renal function is lost).

-Normal kidneys filter about 125 ml/min of creatinine (gives a close estimate to the GFR)

I just want to make sure I've got this straight:

If the normal creatinine clearance is 125 ml/min and that's a close estimate of GFR, then in a diseased kidney the creatinine clearance would be decreased, indicating functional issues with the glomerulus. So a low creatinine clearance = to a higher serum level of creatinine in the blood. Am I on track here, or is there anything I am missing?

Also, what happens if one kidney is removed? I know that the remaining functioning kidney usually does the work of two, but does that involve creatinine as well? Or would it be halved and you would expect to see an increase in the serum level for that person, and it would be the norm for them? I'm assuming it is still 125 ml/hr, but assumptions are never great to make.

Thanks in advance for any answers to my questions!

[JoanRN05]

So.far, so.good! Creatinine clearance (CrCl) is used as an indicator of how well the renals are functioning. It is a more specific indicator of functioning and therefore used to determine medication adjustments. You are correct, USUALLY when you have a very low CrCl, you will see an elevated serum Cr, but that usually takes time, so not a good indicator to eval renal function. This is why the GFR / CrCl are better indicators.

In the case of only one kidney, they often do have permissible elevated serum CrCl, however, it should normalize most of the time as the kidney just responds to what it is filtering. It doesn't "know" the other kidney is gone, it just "sees" higher levels and filters appropriately.

Hope it helps! The kidneys can be tricky guys; super interesting and do a lot for us, so treat them nice! Remember, they are a pressure dependent organ so they need fluid and pressure to function - don't deny them - they will get angry!!

Happy to help if you have more questions! Good luck! ~Thenurseteacher.com

[missmollie, ADN, BSN, RN]

Thank you for your response! Glad I'm on the right track, and I appreciate the answer about the one kidney :)