Kidney growth

[michelf]

Any info on when and how much the remaining kidney grows? (after donation)

[Michael]

I think what you may be after is what happens to kidney function (not so much the size of the kidney) after donation.

As you might guess, overall kidney function drops in half immediately following donation. Within a fairly short period of time--one study calculates the adjustment period being within one week of surgery--the remaining kidney partially compensates so that the average decrease in kidney function is 20% - 30%. That is, a week or so after donation, you would have 70% to 80% of the kidney function you had before donation. Kidney function then continues to decline with age.

Note that these are averages, so some people do better and others do worse. The research has shown that those who tend to have lower kidney function after donation tend to be older and have higher BMIs (Body Mass Index).

By the way, kidney function typically is measured in terms of Glomerular Filtration Rate (GFR). We've had good discussions about post-donation GFR in the past. Here are links to two important--and long--message threads from the old message board:

https://livingdonorsonline.org/cgi/dcforum/dcboard.cgi?az=read_count&om=133&forum=DCForumID13&viewmode=threaded
https://livingdonorsonline.org/cgi/dcforum/dcboard.cgi?az=read_count&om=128&forum=DCForumID13&viewmode=threaded

[WilliamLFreeman]

MSF,

Living kidney donors lose about half of their functioning kidney tissue immediately.  ("About half" because kidneys are never perfectly equal.  Most centers will take the smaller of the 2 kidneys, if the center can see on the CT angiogram or equivalent that 1 is larger that the other.)  However, within about 1-2 months, the remaining kidney "grows" in size (expands), but more importantly increases its functioning.  On average, the increase is to 65% functioning or so of when the donor had 2 kidneys.  (To put in another way, the remaining kidney has increased its function by 30% above what it used to be -- because before donation the 2 kidneys shared the load and thus were not working at maximum possible function.)

Similarly, the recipient's "new/used" kidney also increases its function by almost 30%, so that the recipient's kidney function may get to at least 50-60% of original function.  That level is compared to the level of kidney function on dialysis -- that I have read is only about 10% of original function.  No wonder most recipients feel much better -- more energy, etc. -- after receiving a kidney compared to being on dialysis.

In this and many other ways, our bodies are "pretty cool," no?   

Bill

PS.  The difference in percentage increases given by Michael & I come from differences found in different research studies of different donors.  Not surprising in medical science!

[Michael]

Found another useful message thread from the old message board: https://livingdonorsonline.org/dcforum/DCForumID7/7338.html

[ohtobeahayes]

Our bodies are MAGIC!!!!  If this thread had a like button, I'd hit it!

[Donna Luebke]

I just wanted to comment on the statement that 'the remaining kidney "grows" in size (expands), but more importantly increases its functioning.'  Those who lose a kidney do not all compensate for the loss the same way.  The kidney grows (which is really hypertrophy) because it is one that has to do the work of two. An organ that hypertrophies is not normal even though we consider this a normal response.  Hypertrophy is due to the tubular reabsorption of sodium and to the fact that the 25% of our blood volume that used to be in two kidneys is now being filtered and reabsorbed by one kidney. If we limit our salt or sodium intake, our lone kidney does not have to work so hard. (keep the blood pressure lower, too.)  Does the kidney increase its functioning? We are all different.  The increased functioning is hyperfiltration--hyper again, because one kidney is now doing the work of two.  This does not mean we grow more nephrons in one kidney--the nephrons or renal mass we have lost when we donate does not come back when the lone kidney 'grows.' Donors need to have correct terminology.  Donors need to know what the kidneys do in order to understand what it really means to lose one.  Older or obese donors do not hyperfiltrate as would if younger or thinner and do not recover GFR. Example: If my eGFR was 100 and I donate--I lose 50% of my kidney mass. So the GFR is 50.  Due to hyperfiltration over time, it is assumed my GFR will recover to about 70% of its predonation number.  There is increased concern voiced in the international transplant literature that should not accept donors whose GFR is less than 90.  Those who donate at 80, go to 40 and may not recover GFR then are left with eGFR around 50.  Some believe not hyprfiltrating is good since the kidney is not 'compensating' but maintaining the status quo.  Not an organ under stress.  So much that we could learn from donors if we just followed them. It ia also well-known in the nephrology literature that GFR is an independent risk factor for cardiovascular disease.  So the lower the GFR, the greater the risk.  All the more reason to live a heart and kidney healthy lifestyle per the American Heart Association Guidelines.