Tuesday, October 23, 2012

Do Kidney Donors Have Kidney Disease?

Short answer: We don't know.
Why Don't We Know?
Because after 60 years, we still have no reliable data.

The following are excerpts from Srinivas and Poggio's recent publication:

Unlike any other situation in the practice of medicine, living kidney donors undergo extensive evaluation, with the express and central goal of confirming suspected health instead of suspected disease.

No standardized reference values exist for each of the [GFR determination] procedures used in clinical practice. Thus, the decision of proceeding (or not) with donation is unfortunately often a matter of subjective interpretation rather than more precise science.

It is clear that the creatinine-based GFR estimation equations are not acceptable in the setting of living donor evaluation, mostly because a significant percentage of kidney function needs to be lost before there is a corresponding change in serum creatinine level. 

Although the creatinine clearance always overestimates true GFR..., this method has become the ‘‘standard of care’’ across most transplant centers mostly owing to the lack of a better alternative. This is a good approach as long as the clinician keeps in mind the common potential limitations of this test:
(1) it is reliable only when done properly,
(2) it overestimates GFR by an unpredictable percentage, and
(3) it is not usually interpreted in the context of age- and gender-specific reference values.

Currently, donor renal function is often evaluated without taking into consideration age- and gender-specific reference values, with the result that any value .80 mL/min/1.73 m2 is generally considered appropriate for proceeding with donation.
[Note: Which is exactly what the Joint Societies Consensus Document said, but OPTN stripped it out of the final proposed public policy in 2011]

Thus, the exact magnitude and proportion of risk attributable to donation in the postdonation development of medical conditions cannot be ascertained in the absence of well collected, documented, and retrievable predonation data and equally stringent and complete postdonation follow-up.

...absence of kidney disease or hypertension at the time of donation does not guarantee absence during the life span of the individual.

Thus, when evaluating the 25-year-old donor, one needs estimates of 50- to 60-year risk, not just the estimates of risk obtained from published studies of understandably limited duration (even those with up to 30 years of follow-up). Unfortunately, such data do not exist, and the absence of such data should be emphasized in the informed consent process(emphasis mine)

It is also counterintuitive to think that donation of half of one’s renal endowment would somehow guarantee safe passage in the face of unmonitored (or untreated) postdonation accumulation of comorbidities as donors age.

And there we go, yet another reason why living donors should be given the same 10-year registry as transplant recipients.

Srinivas, T., & Poggio, E. (2012). Do Living Kidney Donors Have CKD? Advances in Chronic Kidney Disease, 19 (4), 229-236 DOI: 10.1053/j.ackd.2012.05.008