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 / Updated  / Source: TODAY
By Dr. Natalie Azar

Kidney stones, known medically as renal calculus or nephrolith, are common and extremely painful. A kidney stone can be as small as a grain of sand, but as large as a golf ball.

They form when substances in the urine become concentrated and harden. The primary cause of kidney stones is dehydration. If someone is not properly hydrated, the body's fluids become more concentrated with dietary minerals, such as calcium. Being dehydrated increases the risk that the minerals will harden into jagged-edged little crystals.

And if you've had one, it's likely you'll have another.

What does a kidney stone feel like?

According to the National Kidney Foundation, symptoms include:

  • extreme pain on either side of your lower back
  • a vague and persistent pain or stomach ache
  • blood in the urine
  • nausea or vomiting
  • fever and chills
  • urine that smells bad or looks cloudy

Kidney stones hurt because they're causing blockage or irritation as they travel down the urinary tract into the ureter. The bigger the stone, the more painful it is. Any kidney stone bigger than 4-5 mm can get stuck.

If you're experiencing symptoms, see a doctor as quickly as possible. Blood and urine tests can determine which type of stone you've got and any diet changes needed. Doctors prefer to let the stone pass on its own, but if it's too large, medical intervention may be needed. Your doctor might prescribe shock wave lithotripsy, an outpatient procedure that breaks up the stones into tiny pieces and is generally considered less risky than surgery.

How can I prevent kidney stones?

First and foremost, make sure you're drinking enough water. You'll want to drink enough so your urine is clear. If it's yellow, you need to drink more. Citrus beverages can help, too. The citrate in the lemonade or orange juice can prevent kidney stone formation.

In addition, certain diet choices can reduce risk. If you've had a kidney stone, limit your sodium intake to 2,300 mg daily, the National Institutes of Health advises. Reducing animal protein in your diet can help.

Foods rich in oxalate — a main ingredient in kidney stones — can also increase risk.

Avoid oxalate-rich foods such as:

  • beets
  • chocolate
  • spinach
  • most nuts

Kidney stones may run in families, but diabetes, obesity and gout can increase the odds of developing a stone. They tend to be more common in men, but anyone can get them, even children as young as 5.

If you're worried you have a kidney stone, it's important you see a doctor right away. The pain can often increase dramatically within a matter of hours and a kidney stone can lead to dangerous complications.