hydration effect on gfr

[kashi416]

Hello, I would like to know what gives like the correct gfr from blood test, is it when you are dehydrated or hydrated or in between. Reason I ask is because 4 months ago my kidney was blocked and I was waiting for surgery and drinking very little because if I drank my kidney hurt. I had two blood test done, I was very dehydrated both times peeing very yellow color urine and my gfr was 79 and 80.
After surgery last week I drank like over a littre of water, peed two times clear urine and then drew blood and my gfr went to 94. So I just want to ask what is my real gfr, did I cheat for 94 or is my real gfr in between like 86?

[bigbuzzard]

The GFR result you get from a single blood test, should really be called 'eGFR' - e=estimated. It's worked out using the creatinine result, plus other factors (including age, ethnicity, sex). And yes, the creatinine result can be affected in the way you describe by your level of hydration. Your 'true' level is probably closer to 94 than 86. The real use of the eGFR is whether it stays roughly the same over time (=good) or reduces (=not so good).

[MatthewC]

If you are dehydrated, such as when having a fasting blood test, then your eGFR will be lower (and creatinine higher obviously), but this is a false result and should be ignored. I have twice had my eGFR measured in such a case - once was pre-op and it gave such a low figure (60) that it would have disqualified me from being a donor if it had been correct. I don't know why they do it if you have been fasting; in fact I commented on this in my blog after a recent check (see http://diaryofakidneydonor.blogspot.co. ... ck-up.html). In that case my eGFR was 53 on the Monday and 45 after fasting on the Wednesday, which is quite a significant difference!

As BB says, the real use of eGFR is to follow a trend and so the important thing is to be consistent in what is done each time, otherwise you are comparing apples and oranges. The eGFR, being an estimate, is not accurate in all ranges, and is most used at lower figures so presumably is more accurate there. Your 80 and 94 are satisfyingly high so I wouldn't worry.

[kashi416]

Ok thanks for replies. I know my gfr is in normal levels, but I need to consider it because my kidney is giving me chronic pain and I believe my only option other than pain killers for rest of my life is kidney removal even though its function is normal.

[foam]

Over the past six months I've had egfr readings of 78, (suffered severe food poisoning here) 65, 54, (sick with an infection here) 90+, 80, (started tacrolimus here) 74. It's pretty variable and random. Over the longer term I've been tested its been very stable in the high 70s for eight years.

[wagolynn]

Ok thanks for replies. I know my gfr is in normal levels, but I need to consider it because my kidney is giving me chronic pain and I believe my only option other than pain killers for rest of my life is kidney removal even though its function is normal.

Pain usually has a cause, has this been investigated?

[kashi416]

Hi, this constant pain is happening since surgery 4 months ago, and no improvment. Whatever I mention as possible cause like surgery inflammation, injured or trapped nerves, scar tissue, adhesions, they just say no way to test it or fix it. Worst is pain is non stop so I constantly have to take opiates or no relief, other medications dont help. Im scared to ask for refill because they will think I am seeking drugs and not take my pain serious anymore. This doctor totally ruined myself, I was thinking about just stent put in and go like that for rest of my life, my family and friends pushed me for surgery saying its no big deal, now when they hear im still in pain they are like you are bullshitting us. Now I only wish they find something on ct scan in two days, otherwise Im going to be stuck with this persistent pain for life

[wagolynn]

If you need the painkillers then ask for more, otherwise they will begin to think the problem has gone.
Lets hope the scan shows something...

[foam]

Over the past six months I've had egfr readings of 78, (suffered severe food poisoning here) 65, 54, (sick with an infection here) 90+, 80, (started tacrolimus here) 74. It's pretty variable and random. Over the longer term I've been tested its been very stable in the high 70s for eight years.

Noticed it has gone up again on today's results despite being quite dry. egfr 86. The tacrolimus has pushed my potassium levels up out of range though, I'll have to watch that.