My grandmother is 79 years old and she has always been in good health. The past few months, however, she has been in and out of the hospital and doctor's office because she gets lightheaded and nauseous. She says she feels like she's going to pass out, and once, she did. The two times she's been in the hospital, the diagnosis has been dehydration, which doesn't make much sense because she drinks water constantly. Some tests were run and everything came back normal, except they found that one of her kidneys was smaller than the other. They said that this could be due to the dehydration, or she could've been born this way. She's a little better now, but she complains that she feels fine while sitting down, but when she stands up she gets nauseous. Her doctor ran some tests and found that her blood pressure drops when she stands up, but they don't know why. Everything else, including cholesterol, heart rate, etc are fine. What could be the problem, and why can't the doctors seem to find out? Thanks for any and all help! :-)

Hey there!

First of all, I want to mention something. As contradictory as this is going to sound, it makes total sense for someone to be dehydrated in the face of drinking tons of water. Believe it or not, if you drink too much water, it actually dehydrates you. What keeps the amount of water you need in your body is salt. Without salt, your kidneys aren't able to reclaim the water that is filtered in to your tubules during the process of your kidneys working. If you drink a lot of free water, all it will do is go to your kidney, be placed in the urine, and it'll go out when you urinate. Also, if you constantly drink a ton of water, you get something called "medullary washout", which destroys the concentration gradient in your kidney and this impairs your ability to reabsorb water....this can cause more water loss!

As for your grandmother....the explanation can STILL be dehydration. The most common reason for blood pressure to drop when you are standing (barring any neurological abnormalities like severe diabetes or parkinson's disease) is volume contraction....i.e. not enough fluid in the body. This is common in older people. They have to assess her volume status which is done clinically...i.e. checking for signs of "dryness" like dry oral cavity, low JVP, orthostatic hypotension (i.e. her blood pressure dropping when she stands up).

Back to your original question though. The fact that she has one kidney smaller than the other could raise suspicion that she has some sort of chronic kidney disease. Does she have any systemic illness? One thing they need to do on her is a urinalysis to see if there is any blood or protein in her urine. Secondly, they have to do a full history and physical to see if she has any signs of chronic disease. (things like diabetes, lupus, high blood pressure etc. can cause kidney problems.).

Additionally, obviously nausea is a very non-specific symptom which can be an indication of many things....nausea is one of the symptoms of chronic renal failure.

People with chronic kidney failure can have any of the following symptoms...please bear in mind that having any of these symptoms doesn't mean you have chronic kidney failure....you have to correlate this stuff with all the different lab tests.

asymptomatic
shortness of breath
ankle swelling
periorbital swelling
nausea
vomiting
fatigue
anorexia (loss of appetite)
pruritis (itching)
malaise (general feeling like crap)

Thank you so much for your reply! Your comment does make perfect sense; I understand that salt is needed to retain water. She's going to the doctor again in a week or two and they're going to do some more testing. She hasn't had any other ailments, and her blood pressure is fine while resting. The doctor can't seem to find anything else wrong with her besides the sudden drop of blood pressure while standing. They've checked for kidney stones and they said they seriously doubt it's kidney failure, but just to be sure we're going to make the doctor check it out. Thanks for your reply, it helped a lot! :-)

Thank you so much for your reply! Your comment does make perfect sense; I understand that salt is needed to retain water. She's going to the doctor again in a week or two and they're going to do some more testing. She hasn't had any other ailments, and her blood pressure is fine while resting. The doctor can't seem to find anything else wrong with her besides the sudden drop of blood pressure while standing. They've checked for kidney stones and they said they seriously doubt it's kidney failure, but just to be sure we're going to make the doctor check it out. Thanks for your reply, it helped a lot! :-)
No problem!

I do want to qualify one o' my statements.....I would say that 75-80% of the water we absorb in our bodies, we need salt for....there is an area at the collecting duct (just before the urine is collected to go to the renal pelvis and then the bladders) that can absorb free water, but it's not as significant as the other form of reabsorption.

The first thing I'd think about if someone was having a drop in blood pressure when standing up is volume contraction....I don't understand how the doctor would go from "orthostatic hypotension" directly to thinking about kidney failure. There's so much other stuff that could be going on.

A quick three things that can be done to check to see how the kidneys are functioning are serum urea and creatinine, urinalysis and a kidney ultrasound. It's imperative, though, that the simple things are ruled out first.