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  1. Carl
  2. General Nephrology Questions
  3. Thursday, 24 January 2019
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Hello, I'd like to ask two questions:

1) I've just read the article by Dr. Jordan Weinstein titled "What is the importance of the albumin-to-creatinine ratio".
I would like to know why the albumin-creatinine ratio is considered an alternative to a 24-hour urine protein. I understand the explanation that the albumin-creatinine ratio cancels out variations in concentration of the urine, but why would a ratio be equivalent to an absolute amount? The albumin-creatinine ratio divides the concentration of albumin in a spot urine sample by the concentration of creatinine in the same sample. Once you divide these two values, you end up with a ratio, not the absolute amount of albumin in the spot urine sample. The ratio will be lower than the actual amount of albumin in that sample. Why is this ratio equivalent to the absolute amount of albumin in a 24-hour urine sample?

2) Are there any laboratory tests (blood tests) that can be used to differentiate Acute Kidney Injury from Chronic Kidney failure? In both cases, I suppose the creatinine, BUN, and eGFR would be abnormal, right? If that is correct, what blood tests can be used to differentiate one from the other?

Thanks.

Carl.
Responses (2)
Accepted Answer Pending Moderation
1) The albumin to creatinine ratio shows us how much protein is excreted with each mmol (or gram depending on the units) of urinary creatinine. So far example, if the ACR is 10 mg / mmol, then each mmol of creatinine is accompanied by 10 mg of albumin in the urine. Most people excrete 10-15 mmol of creatinine per day. Therefore, the total 24 hr protein can be estimated by multiplying the ACR x the amount of creatinine excreted - so in this case 12.5 mmol creatinine x 10 mg albumin/mmol creatinine = 125 mg per 24 hr period.

2) There are no reliable tests to distinguish acute from chronic kidney disease. A PTH level can sometimes be helpful as severe(5-10 fold) increases in this hormone is usually only seen in chronic kidney disease. An abdominal ultrasound showing small echogenic kidneys can be useful to establish chronic kidney disease.


Dr. Jordan Weinstein
Accepted Answer Pending Moderation
Thank you very much.
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