I am a 64 year old Canadian male, no diabetes, with well controlled hypetension 117/70-75 with Losartan and Norvasc. 14 years ago, my kidney function went from 62-64 to 56-57. My PCP said no problem but I insisted on a nephrologist consult. All bloodwork, urinalysis, and ultrasound were deemed normal. Since that time my GFR fluctuated between 57 and 64. Last year, my GFR suddenly showed a decline to the 53-58 range. Again, my PCP said normal aging (as aging is a component of the GFR calculation and GFR declines with age) but again I asked for a nephrologist consult. My 24 hour urine and urinalysis and a detailed bloodwork analysis were again deemed normal for protein, electrophoresis, etc. My nephrologist said my PCP was right. The decline can correctly be referred to as aging decline. She noted that in the last fourteen years my creatinine varies between 114 and 126 umol/L and this is reflected in the GFR fluctuation. I asked her if this is classified as CKD and she said by the strict KDIGO guidelines, that would be true. I follow a strict low salt diet, similar to DASH. I monitor my BP bi-weekly and ensure I don’t overeat. I don’t smoke and have the rare glass of wine. I maintain my body weight carefully (I am 5 foot 5 inches and weight 132lbs). My question, is it normal for creatinine to fluctuate in such a range? Can my GFR decline correctly be referred to as caused by aging?

The estimated glomerular filtration rate (eGFR) is used to classify the Stage of chronic kidney disease (CKD) but it cannot make a specific diagnosis as to the cause of CKD. In your case, you would technically be at Stage 3a of CKD but I cannot identify a specific cause for your disease. It sounds like you are doing all of the correct things to prevent further loss of kidney function. It is true that kidney function declines with aging and this averages about 1% loss per year after age 40. The variability that you describe is very normal. It is common for the laboratory to report serum creatinine that varies by plus or minus 10 micromole per liter (umol/L) from one day to the next. You may have kidney disease related to your hypertension, but your current management is exemplary and you should continue your present lifestyle management and annual assessment of your kidney function.

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