How do I prevent another kidney stone?

DEAR DOCTOR K:

I recently had a very painful kidney stone. What can I do to prevent another?

DEAR READER:

First of all, my sympathies: Pain from passing a kidney stone can be as bad as any kind of pain.

Kidney stones are hard, chemical deposits that form inside the kidney chambers where urine is collected. Urine passes from the kidney down a narrow tube (the ureter) and into the bladder. If a stone gets carried into the narrow ureter, it can get stuck. This can cause severe pain, bloody urine, nausea and vomiting.

If you’ve had one kidney stone, you’re at increased risk for another. That’s because you probably have a tendency (based on your genes, your diet or both) to form kidney stones.

New guidelines say the best way to prevent a second kidney stone is to drink lots of water every day. Keeping your urine diluted makes it harder for stones to form.

The guidelines are based on clinical trials of treatments and diet changes that doctors commonly recommend to help prevent second kidney stones. The researchers found enough evidence to say that drinking lots of fluids reduces the risk of a second kidney stone.

They did not find enough evidence to recommend other treatments or diet changes — but that’s not the same as finding evidence that other treatments don’t work.

I still plan to recommend the following steps to help prevent even a first kidney stone. These are all healthy suggestions, whether or not they actually prevent kidney stones:

  • Drink enough water. If you have had a kidney stone, drink enough liquids to pass two quarts (8 cups) of urine a day. Include citrus drinks, such as lemonade and orange juice. The citrate in these beverages helps to stop stones from forming.
  • Eat calcium-rich foods. Most kidney stones contain calcium, which usually hooks up with a chemical called oxalate. The calcium in foods and drinks binds to the oxalate inside the gut and passes out of the body in a bowel movement. As a result, less calcium goes out in the urine. This reduces the chance that stones will form.
  • Decrease sodium (salt) in your diet. A high-sodium diet can trigger kidney stones because it increases the amount of calcium in your urine. If you have had a kidney stone, limit daily sodium to 1,500 milligrams (mg).
  • Limit animal protein. Eating too much animal protein increases the amount of uric acid in the urine. This can cause uric acid stones. It can also trigger formation of stones that contain calcium. A high-protein diet also reduces levels of citrate, which helps prevent stones from forming.
  • Limit stone-forming foods if you have had kidney stones. If you were able to collect the stone in your urine after it was passed, and your doctor examined it and said it was a calcium oxalate or calcium phosphate stone, limit oxalate- and phosphate-containing foods like beets, chocolate, spinach, rhubarb, tea, most nuts and colas.

Fortunately, I’ve never suffered from a kidney stone. But if I had — based on what my patients have told me — I would do anything to avoid a second.