Kidney Stone Causes

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.

Different things can bring on kidney stones, including what you eat and certain medications. If you or someone in your family has had a kidney stone, you’re more likely to have them.

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.

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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.

Diet

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:

  • Spinach

  • Rhubarb

  • Grits

  • Bran cereal

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.

Gut problems

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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.

Obesity

You’re almost twice as likely to get a kidney stone if you’re obese. That’s when your body mass index is 30 or above. If you’re 5-foot-10, obesity starts at 210 pounds.

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.

Certain genetic diseases. One example is medullary sponge kidney, a birth defect that causes cysts to form in the kidneys.

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.

Hyperparathyroidism. Your parathyroid glands can pump out too much hormones, which raises calcium levels in your blood and urine.

Renal tubular acidosis. This kidney problem causes too much acid to build up in the body.

Medications

Some that can cause stones include:

WebMD Medical Reference Reviewed by Neha Pathak, MD on August 10, 2020

Sources

SOURCES:

Harvard Medical School: “Kidney Stones,” “5 Steps to Preventing Kidney Stones.”

The University of Chicago: “Why Do Kidney Stones Cause Pain?”

Urology Care Foundation: “Kidney Stones: What You Should Know,” “What Causes Kidney Stones?”

National Kidney Foundation: “Kidney Stones,” “Diet and Kidney Stones.”

Crohn’s and Colitis Foundation: “Kidney Disorders Fact Sheet.”

Johns Hopkins Medicine: “Obesity-Mild or Severe-raises Kidney Stone Risk,” “Roux-En-Y Weight Loss Surgery Raises Kidney Stone Risk.”

Up-to-Date: “Patient education: Primary hyperparathyroidism (Beyond the Basics),” “Dietary factors and medical problems that increase the risk of kidney stones.”

University of Wisconsin Health: “Disease-related Contributors to Kidney Stones,” “Medication Contributors to Kidney Stones.”

Mayo Clinic: “Kidney Stones” “Symptoms and Causes”

American Kidney Fund: “Kidney Stone Causes, Symptoms, Treatments, & Prevention”

National Institute of Diabetes and Digestive and Kidney Diseases: “Renal Tubular Acidosis”

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