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Living Donor Research Living Donor Risks Living Kidney Donor

Living Kidney Donor Blood Pressure, Plasma Arginine & Glomerular Filtration Rate

Two living kidney donor related publications hit the google alerts this weekend.

 

The first, from Serbian researchers, observes that not only does renal function (GFR) decrease abruptly following live donor nephrectomy, so does plasma arginine.

 

Arginine is an animo acid. It plays an important role in cell division, wound healing (which requires cell division), removing ammonia (a toxin) from the body, immune function and the release of hormones.

Supplements of L-Arginine have been shown to reduce blood pressure in folks with hypertension.

 

The authors concluded:

Unilateral nephrectomy causes an early abrupt decrease in plasma arginine and reduction in glomerular filtration rate in LKDs that was associated with increased net protein breakdown in the peripheral tissues and elevated oxidative damage, which has to be considered in their therapy.

 

The second bit of living kidney donor related health news comes from a presentation at the 28th Annual Scientific Meeting of the American Society of Hypertension. A group of physicians at a U.S. transplant center observed that living kidney donors with ‘elevated’ systolic blood pressure (the top/upper number) “had a significantly greater number of potentially adverse cardiovascular (CV) and renal risk factors compared with the donors who had lower” systolic blood pressure (SBP).

The operative word here is ‘elevated’. Systolic blood pressure of 140 or greater is considered hypertensive. These researchers looked at living kidney donors with SBP of 115-139, because other clinical studies (of non-donors) have indicated that  SBP of 115 of higher suggests an increased risk of cardiovascular disease and events.

 

“Elevated blood pressure even within the non-hypertensive range could thus be reflective of a latent risk for adverse cardio-metabolic outcomes in living kidney donors, the early recognition of which could support closer monitoring of such individuals for eventual cardiovascular abnormalities.”

 

 

Just to tie all this together:

– protein in the urine is a symptom of kidney damage, so something we living kidney donors have to protect against.

– a drop in arginine post-nephrectomy coincides with an increase in protein breakdown

– arginine also reduces blood pressure

Meanwhile…

– reduced kidney function is associated with higher risk of cardiovascular disease and risks

– living kidney donors also exhibit an increase in systolic blood pressure post-donation

– an elevated SBP of 115-139 (in anyone) is associated with greater cardiovascular disease and events.

– living kidney donors with an SBP of 115-139 are exhibiting more cardiovascular events.

 

Take care of yourself, kids!

Categories
Living Donor Research Living Donor Risks Living Kidney Donor

LKD Eval Document’s Notes on Hypertension, Proteinuria and GFR

Thirty pages is a lot to filter through, especially if one is lacking context or familiarity with the process or vocabulary of transplant. But where this document becomes interesting and somewhat important is in its appendicies. The information about hypertension, proteinuria, kidney function (GFR) etc, is more than is shared with prospective living donors and if known, can help a living donor candidate to protect themselves and make the best decision possible for their future health.

For example (page 19):
Caucasian hypertensive donor candidates younger than age 50 and non-Caucasian donors at any age with hypertension have a greater lifetime risk of ESRD and may not be suitable candidates for unilateral nephrectomy.

 

 

Proteinura (page 20): The most reliable way to measure urinary protein or albumin is by a timed urine collection with the albumin excretion rate reported per unit time or per gram of creatinine. Microalbuminuria is defined as urine albumin excretion > 30 mg < 300 mg/day in both men and women or > 17 < 250 mg/gm creatinine in men and > 25 < 355 mg /gm creatinine in women. Clinical proteinuria is defined as protein excretion > 300 mg/day in both men and women or > 250 mg/gm creatinine in men and > 355 mg /gm creatinine in women

 

GFR, or renal function (page 21):
Ideally, kidney function should be assessed with a technique, which directly measures GFR using inulin, an iodinated tracer or a radioactive tracer. However, these techniques are not widely available, and a 24-hour urine collection to calculate creatinine clearance is an acceptable alternative. The adequacy of the 24-hour collection should be confirmed by assessing whether it contains 20-25 mg creatinine/kg body weight for men and 15-20mg/kg for women. The use of a serum creatinine alone, even if converted to an estimated GFR using one of the currently available formulas, is not sufficient.

 

The biggest revelation is as follows:

Kidney function usually declines with aging, so cut-offs to accept a donor should vary based on age.

 

If you’d like, conduct a experiment. Search for the major transplant related websites (those with info about living donation) and see what they say about pre-donation GFR in prospective kidney donors.

Does it say the minimum cut-off is a GFR is 80? Now refer back to the italicized statement.

To whit: A GFR of 85 would be of less concern for a 60 year old man, since that value is above average for that age and there is less remaining lifetime for GFR to decline. In contrast, the same GFR of 85 approaches two standard deviations below the mean in a 25-year-old donor.

And the whizbang climax: It is recommended that potential donors have measured GFR that is one standard deviation below the mean for the donor’s age.

 

So what is the mean GFR corresponded to age? The document includes a table based on two studies, which I’m including below.

The standard deviation is a bit harder to pin down. Mathematically, standard deviation is a measure of how spread out the data set is. One standard deviation encompasses approximately 68% of the data set while two standard deviations includes roughly 95% of the total data.

I obtained the referenced 2009 study, which contains a plethora of its own graphs and tables. It repeatedly addresses “upper and lower limits of normal values” which they peg at the 5th and 95th* percentile (The measure used by the Cleveland Clinic and Mayo Clinic), but never addresses standard deviation. It still has its uses though – see below (click for enlargement)

Living donors generally have the I-Iothalamate GFR done, which is the first set of numbers not in parenthesis. Bear in mind these are PRE-donation numbers, and it’s safe to say that the one standard deviation referred to in the consensus document would be higher than the 5th percentile listed here.

Compare these numbers to the one-size-fits-all 80 GFR cut-off currently used by the transplant industry. Think there’s a big gap there? So do I.

 

*Because really high GFR can be indicative of other disease related issues, believe it or not.

Poggio, E., Rule, A., Tanchanco, R., Arrigain, S., Butler, R., Srinivas, T., Stephany, B., Meyer, K., Nurko, S., Fatica, R., Shoskes, D., Krishnamurthi, V., Goldfarb, D., Gill, I., & Schreiber, M. (2009). Demographic and clinical characteristics associated with glomerular filtration rates in living kidney donors Kidney International, 75 (10), 1079-1087 DOI: 10.1038/ki.2009.11