Harvard Health Blog
If you've ever passed a kidney stone, you probably would not wish it on your worst enemy, and you'll do anything to avoid it again. "Kidney stones are more common in men than in women, and in about half of people who have had one, kidney stones strike again within 10 to 15 years without preventive measures," says Brian Eisner, M.D., co-director of the Kidney Stone Program at Harvard-affiliated Massachusetts General Hospital.
Where do kidney stones come from?
Kidney stones form when certain substances, such as calcium, oxalate and uric acid, become concentrated enough to form crystals in your kidneys. The crystals grow larger into "stones." About 80 percent to 85 percent of kidney stones are made of calcium. The rest are uric acid stones, which form in people with low urine pH levels.
After stones form in the kidneys, they can dislodge and pass down the ureter, blocking the flow of urine. The result is periods of severe pain, including flank pain (pain in one side of the body between the stomach and the back), sometimes with blood in the urine, nausea, and vomiting. As the stones pass down the ureter toward the bladder, they may cause frequent urination, bladder pressure, or pain in the groin.
"If you experience any of these symptoms, see your primary care physician," says Eisner. "He or she will likely perform a urinalysis and a renal ultrasound, abdominal X-ray, or CT scan to confirm kidney stones are the source of your pain and determine their size and number."
Let kidney stones pass
Stones typically take several weeks to a few months to pass, depending on the number of stones and their size. Over-the-counter pain medications, like ibuprofen (Advil, Motrin IB), acetaminophen (Tylenol), or naproxen (Aleve), can help you endure the discomfort until the stones pass. Your doctor also may prescribe an alpha blocker, which relaxes the muscles in your ureter and helps pass stones quicker and with less pain.
If the pain becomes too severe, or if they are too large to pass, they can be surgically removed with a procedure called a ureteroscopy. Here, a small endoscope (a device with a miniature video camera and tools at the end of a long tube) is passed into the bladder and up the ureter while you are under general anesthesia. A laser breaks up the stones, and then the fragments are removed.
Take steps to bypass kidney stones
Even though kidney stones can be common and recur once you've had them, there are simple ways to help prevent them. Here are some strategies that can help:
1. Drink enough water. A 2015 meta-analysis from the National Kidney Foundation found that people who produced 2 to 2.5 liters of urine daily were 50 percent less likely to develop kidney stones than those who produced less. It takes about 8 to 10 8-ounce glasses (about 2 liters total) of water daily to produce that amount.
2. Skip high-oxalate foods. Such foods, which include spinach, beets and almonds, obviously raise oxalate levels in the body. However, moderate amounts of low-oxalate foods, such as chocolate and berries, are OK.
3. Enjoy some lemons. Citrate, a salt in citric acid, binds to calcium and helps block stone formation. "Studies have shown that drinking 1/2 cup of lemon juice concentrate diluted in water each day, or the juice of two lemons, can increase urine citrate and likely reduce kidney stone risk," says Eisner.
4. Watch the sodium. A high-sodium diet can trigger kidney stones because it increases the amount of calcium in your urine. Federal guidelines suggest limiting total daily sodium intake to 2,300 milligrams (mg). If sodium has contributed to kidney stones in the past, try to reduce your daily sodium to 1,500 mg.
5. Cut back on animal protein. Eating too much animal protein, such as meat, eggs and seafood, boosts the level of uric acid. If you're prone to stones, limit your daily meat intake to a quantity that is no bigger than a pack of playing cards.
(Matthew Solan is executive editor of Harvard Men's Health Watch.)