Saturday, December 6, 2008

CKD in the Elderly

A current controversy in the CKD community involves definitions of CKD in the elderly. The issue is not trivial: were we to apply the standard KDOQI definitions of CKD staging, using the MDRD equation to estimate GFR, this would lead to a diagnosis of CKD in 47% of the U.S. population! Do nearly half of the geriatric population deserve to be labeled as having a disease of the kidneys? Or should this decrease in GFR be merely considered a normal consequence of aging?

In favor of labeling this decreased GFR in the elderly as abnormal, histopathologic analysis of geriatric kidneys shows evidence of microvascular disease that in a young person would not be seen as normal. Mortality does seem to correlate with GFR, even in the mid-range. Also, from a historical perspective, the idea that hypertension was driving conditions such as stroke and cardiovascular disease was initially dismissed based on how common it was in the general population; the same situation could conceivably be the case here. A good review, from a 2005 NEJM article, is found here.

In opposition to this, Drs. Glassock and Winearls rebuttal in this month's AJKD take issue with the use of the pejorative term "disease" to describe such a large fraction of the nation's elderly, and suggest instead to use the term "age-related reduced kidney function."

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