Causes of Kidney Stones
Kidney stones happen when your pee has a high concentration of minerals and other substances -- like calcium, oxalate, and uric acid -- that come together to make crystals. Crystals stick together to make one or more stones. Stones happen when your urine doesn’t have enough fluid and other substances to keep them from happening.
A kidney stone can be as tiny as a grain of sand, and you can pass it without ever knowing. But a bigger one can block your urine flow and hurt a lot. Some people say the pain can be worse than childbirth.
Types of Kidney Stones
The different types of stones are made of different types of substances. It's important to know the type of stone you have, so you can know what may have caused it and how to prevent it.
If you pass a kidney stone, you should take it to your doctor so they can send it to the lab and find out what kind it is:
Calcium stones. Most kidney stones are made from calcium, in the form of calcium oxalate. There are two kinds of calcium stones:
Calcium oxalate. Oxalate is a substance made daily by your liver. Some fruits and vegetables, as well as nuts and chocolate, are high in it. Your body absorbs the substance when you eat these foods. Other things that can make the concentration of calcium or oxalate in your urine to rise are taking high doses of vitamin D, intestinal bypass surgery and certain metabolic disorders.
Calcium phosphate. This type of stone happens more often in people with metabolic conditions, like renal tubular acidosis (where your kidneys aren’t able to help maintain proper acid balance in your blood) or with people who take medications to treat migraines or seizures.
Struvite stones. These can form from a urinary tract infection (UTI). The bacteria that cause the infection make ammonia build up in your urine. This leads to formation of the stones. The stones can get large very quickly.
Uric acid stones. These form in people who lose too much fluid because of chronic diarrhea or malabsorption; eating a high-protein diet; or having diabetes or metabolic syndrome. Certain genetic factors also may increase your risk of uric acid stones.
Cystine stones. This rare type of stone forms because the kidneys leak too much of a specific amino acid called cystine into the urine. They occur in people with a genetic disorder called cystinuria.
Factors that Increase Your Risk of Kidney Stones
Kidney stones often have no single cause, and several factors may increase your risk for getting them. Some of these factors are listed below. They include:
Lack of water
You need to make enough pee to dilute the things that can turn into stones. If you don’t drink enough or sweat too much, your pee may look dark. It should be pale yellow or clear.
If you’ve had a stone before, you should make about 8 cups of urine a day. So aim to down about 10 cups of water daily, since you lose some fluids through sweat and breathing. Swap a glass of water for a citrus drink. The citrate in lemonade or orange juice can block stones from forming.
What you eat can play a big role in whether you get one of these stones.
The most common type of kidney stone happens when calcium and oxalate stick together when your kidneys make urine. Oxalate is a chemical that’s in many healthy foods and vegetables. Your doctor may tell you to limit high-oxalate foods if you’ve had this type of stone before. Examples include:
You may have heard that drinking milk can bring on kidney stones. That’s not true. If you eat or drink calcium-rich foods (like milk and cheese) and foods with oxalate at the same time, it helps your body better handle the oxalate. That’s because the two tend to bind in the gut instead of in the kidneys, where a stone can form.
Sodium. You mainly get this through table salt. It can raise your chances of getting several types of kidney stones. So watch out for salty snacks, canned foods, packaged meats, and other processed foods.
Animal protein. One kind of kidney stone forms when your pee is too acidic. Red meat and shellfish can make uric acid in your body rise. This can collect in the joints and cause gout or go to your kidneys and make a stone. More importantly, animal protein raises your urine’s calcium level and lowers the amount of citrate, both of which encourage stones.
Stones are the most common kidney problem in people with inflammatory bowel disease like Crohn’s disease and ulcerative colitis. Bowel problems can give you diarrhea, so you make less pee. Your body may absorb extra oxalate from the intestine, so more gets in your urine.
Weight loss surgery can help you shed pounds and improve your health. But studies suggest that people who have the most common weight loss operation, the Roux-en-Y gastric bypass, are at a higher risk of stones. Not every weight loss surgery carries this risk, only the ones that cause malabsorption.
Other medical conditions
Many diseases can play a role in one or more types of kidney stones to form.
Type 2 diabetes. It can make your urine more acidic, which encourages stones.
Gout. This condition makes uric acid build up in the blood and form crystals in the joints and the kidneys. The kidney stones can become large and very painful.
Renal tubular acidosis. This kidney problem causes too much acid to build up in the body.
Some that can cause stones include: