Kidney Health

Kidney Stones

May 5, 2010

Kidney Stones

After passing my Internal Medicine Board Recertification, I started intensively studying for my Nephrology Board Exam. After reviewing the kidney stone section, I wanted to share some pearls of wisdom regarding the two common questions I often hear when evaluating a patient with kidney stones.

First, I want to make sure you know the difference between a urologist and a nephrologist because both specialties help patients with kidney stones. Urology is the branch of medicine that deals with the diagnosis and treatment of diseases of the urinary tract and urogenital system. Nephrology is the science that deals with the kidneys, especially their functions or diseases. Urologists perform surgery to remove stones. Nephrologists do not perform surgery. Instead, kidney doctors focus on why the patient is prone to get stones. This evaluation is called a “metabolic work up.” Frequently the nephrologist and urologist work together to provide a patient with total kidney stone care.

The only universal recommendation I make to my kidney stone patients is that they need to drink enough water so that they produce more than two liters of urine per day. The water ingestion should be throughout the day. The urine concentration needs to be dilute so that the risk of kidney stone formation is decreased. Here’s why: let’s say a person is prone to make calcium oxalate stones — a frequent type of kidney stone. In order for the calcium to attach to the oxalate, the two molecules have to get “near enough” to each other.

| calcium –> <– oxalate | 
A concentrated urine. Easier for calcium and oxalate to find each other.
| calcium –> <–oxalate | 
A dilute urine. Harder for calcium and oxalate to find each other. Decreases the likelihood of stone formation.

Unfortunately, kidney stone evaluation is not that simple. You have to take into account the “saturation risk” of the two molecules joining. Simply stated, there is other “stuff” in the urine which may increase the likelihood of the calcium binding with the oxalate. A super-saturation profile gives us this necessary information:

| calcium –> <– oxalate | 
This urine has 1 time the risk of forming a kidney stone.
| calcium –> <– oxalate | 
This urine has 3 times the risk of forming a kidney stone — even though the amount of urine is the same as the sample above!

Therefore, I recommend you come to me for a kidney stone evaluation prior to altering your approach to reducing your kidney stones. You want to make sure you are doing the right thing prior to making a lifestyle intervention. I’ve seen people inadvertently INCREASE their risk, and I don’t want that to happen to you.

Now we can answer the questions:

Can vitamin C lead to kidney stones?
Yes it can, but in high doses. High amounts of vitamin C increase the oxalate production in the body. Therefore, more oxalate is excreted in the urine, and in some cases the risk for kidney stones (nephrolithiasis) increases!

What about calcium supplements?
NO! Turns out that calcium when eaten with meals binds the oxalate you eat IN THE GUT, so the oxalate is less absorbed and you decrease your risk for kidney stone formation! What you have heard all these years turns out to be a myth!

One Comment
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    Mitch Cruse

    Thank you Dr Aaronson for the information, I just had a minor proceed performed based on my family doc recommendations to see if kidney stones were causing some of my stomach pains? It turned out that I have 3 small hernias. While I know I don't drink enough water, after reading your pearls of wisdom, I'm heading off to fill my water jug! Preventative maintenance, exercise and education are crucial to a long healthy life! Thank you, Mitch

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