Kidney stones vary in size and shape—they can be as small as a grain of sand or grow to be as large as a pearl. They’re a very common urinary tract condition, affecting about 1 in 10 people in the US.
What is a kidney stone?
A kidney stone is a small, hard lump that forms in your kidney when normal substances in your urine become highly concentrated.
Stones can stay in your kidneys, undetected, until they start to pass through your ureters, which are the tubes that run from your kidneys to your bladder. The stone will pass through your ureters and out of your body in your urine.
Passing can be very painful and sometimes complicated. While many people stay home to pass a stone, some may need professional assistance when they start to experience symptoms like nausea, vomiting, and fever.
Types of Kidney Stones
There are four major types of stones:
- Calcium stones:
These are the most common type of kidney stones. An estimated four out of five kidney stones are calcium stones. They occur in two forms: calcium phosphate and calcium oxalate. Calcium oxalate stones are more common because they are usually caused by high oxalate excretions, whereas calcium phosphate stones are the result of high level of calcium and a high pH level in your urine. - Uric acid stones:
These stones can form when your urine is frequently acidic. Uric acid in your urine may be increased when you eat a diet that is rich in purines. Purines are substances found in fish, shellfish, and animal protein. When uric acid is concentrated in your urine, it can settle and form a stone either by itself or with calcium. - Struvite stones:
Urinary infections can cause struvite stones to form when bacteria makes ammonia that builds up in your urine. This type of stone is made up of ammonium, phosphate, and magnesium. Struvite stones grow large quickly and can form without warning or symptoms. After eliminating the infected stones, the best way to prevent others from forming is by staying free of infection. - Cystine stones:
A genetic disorder that causes cystine to leak from your kidneys into your urine forms crystals that usually come together to form stones. This type of stone is rare, however.
Preventing Kidney Stones
If you’ve had kidney stones in the past, you’re at high risk of experiencing them again. The best way to prevent stones is to drink a lot of fluids every day. If you haven’t yet experienced stones, you should drink enough water to produce two liters of urine, but if you’ve had them before, drink 8 to 12 glasses of water per day.
If your doctor is able identify the type of your kidney stone, a specific diet can be designed for you to help prevent the formation of other stones. For those with a health condition that puts you at risk of kidney stones, medicine prescribed by your doctor can treat the condition.