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Kidney Stones

What Are Kidney Stones?

Kidney stones are small, solid masses that can build up in a person's . They're hard, like little stones, but are actually crystals that form when salts and minerals in urine (pee) become extra-concentrated. Over a few weeks or months, these crystals can sometimes build up in the kidneys to become stones.

Kidney stones mostly happen to adults, though teens can get them.

Kidney stones range in size from a fraction of an inch to several inches. Very small stones (like those that are less than ¼ inch or about 5 mm in size) usually can pass through the urinary tract and out of the body on their own with little or no pain. Larger stones can be quite painful, though. They may block the flow of urine and cause other urinary tract problems. Luckily, it's rare for kidney stones to do permanent damage, and doctors have lots of ways to treat them.

There are several kinds of kidney stones with many different causes. Because of this, doctors treat them based on what kind they are — and how big. Some people just need to drink a lot of water and take pain medicines to help a kidney stone pass out the body naturally. Others might need surgery or another medical procedure.

How Do Kidney Stones Happen?

Our kidneys work a lot like a garbage collection and disposal system, removing extra fluids and waste products from the blood. These wastes leave the body as urine.

Urine contains things like calcium, phosphate, and uric acid. Usually, these substances are very diluted so they flow through the urine easily. But if urine becomes concentrated or something changes the level of a substance in the urine, crystals might form. The crystals can become lodged in kidney tissue and grow to become kidney stones.

Types of Kidney Stones

There are four major kinds of kidney stones:

  1. Calcium stones. The most common kind of kidney stone, these develop when calcium in the urine combines with other substances to form crystals.
  2. Uric acid stones. This type of stone forms when there is too much uric acid in the pee. Uric acid can crystallize by itself or combine with calcium to form a stone.
  3. Struvite stones (also called staghorn calculi because they look like a stag's antlers). These stones can grow rather large. They're made of a mineral called struvite, which is a combination of ammonium, magnesium, and phosphate.
  4. Cystine stones. This rare type of stone forms if someone has too much of an amino acid called cystine in the urine.

What Causes Them?

Most teens who get kidney stones have a health condition that increases their risk of developing them. Sometimes it's not clear what caused someone's kidney stones, but doctors can still treat them.

Some types of kidney stones run in families. If a relative has had kidney stones, you may be more likely to develop them at some point. People who have had kidney stones in the past have a higher chance of getting them again.

Here are some reasons why people develop kidney stones:

  • Dehydration. When someone doesn't drink enough fluids, it can cause urine to become extra-concentrated. This increases the chance of crystals forming.
  • An unhealthy diet and lifestyle. Drinking sugary or caffeinated drinks and eating a diet high in sodium (salt) can increase the risk of calcium stones. Obesity also can make someone more likely to get them.
  • Urinary tract problems. Some people have a defect in the urinary tract that blocks the flow of urine and creates an area where it sits in a tiny pool. When this happens, crystal-forming substances may settle together and form stones. Sometimes people (especially women) with kidney and urinary tract infections (UTIs) can develop struvite stones.
  • Certain medications. Some prescription and over-the-counter medicines may cause kidney stones if taken in large doses.
  • Metabolic disorders. If the body has trouble breaking down and using food, it can lead to concentrated levels of calcium or cystine in the urine.
  • Cystinuria. This genetic condition causes too much cystine to pass from the kidneys into the urine, causing cystine stones to form.
  • Other medical conditions. A number of diseases and conditions can increase the risk of kidney stones. These include gout, other diseases of the kidneys, conditions that affect the thyroid or parathyroid gland, and some UTIs.

What Are the Symptoms?

Usually, people with kidney stones won't notice them until the stones move around in the kidney or pass into the ureter. Small stones may move through the urinary tract and out of the body with no problems. Larger stones, though, can block the urinary tract and cause symptoms like these:

  • a sharp pain that starts in the side or back
  • pain that spreads to the lower belly and groin as stones move through the urinary tract
  • pain that comes and goes in waves
  • blood in the urine (red- or brown-colored pee)
  • nausea and vomiting
  • needing to pee often or urgently
  • fever or chills

If a stone is too large to move, it might cause a blockage called hydronephrosis (hye-drow-nuh-FRO-sis). Hydronephrosis is when one of the kidneys swells from a backup of urine. Someone with hydronephrosis might feel side or back pain. Doctors can tell if someone has it through imaging tests (like X-rays, ultrasound, or CT scans). If it's not treated, it can lead to long-term kidney damage.

If you feel pain in your side, see blood in your urine, or have other symptoms of kidney stones, talk to your mom or dad and make an appointment to see a doctor as soon as possible. If you are in pain and also feel nauseated, throw up, have fever or chills, or have trouble peeing, go to an emergency clinic or hospital ER.

What Do Doctors Do?

Your doctor will examine you and ask about the symptoms and how long you've had them. The doctor may also ask questions about your lifestyle, like what kinds of things you eat and drink. The doctor will also be interested in your family medical history, such as whether any relatives have had kidney stones or other diseases or conditions that affect the kidneys or urinary tract.

If the doctor thinks you have a kidney stone, you'll probably have blood, urine, or kidney function tests. You also might undergo imaging tests, which can show a stone's exact size and location. This information helps doctors provide the best treatment.

Treating Kidney Stones

Small stones usually work their way out of the body without much treatment. Large stones may need to be treated with surgery or another procedure.

To help a small stone pass out of your body, the doctor will probably tell you to drink plenty of water. Doctors may prescribe medications for pain, but over-the-counter medicines (like ibuprofen and acetaminophen) are usually enough to ease any pain from small stones.

The doctor may ask you to pee through a strainer for a few days to collect kidney stones as they come out your body. Doctors send the stones to a lab for testing to find out which minerals make up the stones. Knowing this helps doctors decide the best way to treat them.

Sometimes kidney stones require a hospital stay. If stones block the urinary tract or cause severe pain or dehydration, patients need intravenous (IV) fluids and pain medications to stay hydrated and help the stone pass through the urinary tract.

Large stones don't usually pass out of the body on their own. Doctors need to break them up into smaller pieces or remove them in one of several ways:

  • Using sound waves or shock waves to break kidney stones into small pieces. These pieces can be passed out of the body in the urine (this process is called extracorporeal shock wave lithotripsy).
  • Using a ureteroscope to find and break up kidney stones. A ureteroscope is a small tube with a camera at the end. Doctors give the patient anesthesia, then thread the tube into the urethra and up into the urinary tract until they locate the stone. The ureteroscope has special tools that can remove the stone from the urinary tract or break it into smaller pieces.
  • Using surgery to remove large stones. If someone has large stones in or near the kidneys, doctors do surgery. The most common type of surgery is a procedure called nephrolithotomy. After giving anesthesia, the surgeon makes a small cut in the patient's back and inserts a tube called an endoscope into the kidney to remove or break up the stone. People often stay in the hospital for a couple of days after kidney stone surgery.

Preventing Kidney Stones

It's not always possible to prevent some types of kidney stones. The best thing you can do is drink enough water to avoid dehydration. If your urine is almost clear, it's a sign that you're getting enough fluids. Another thing all teens can do is cut back on salt and salty foods.

If you've had kidney stones in the past, your doctor will want you to drink plenty of fluids — about 8 cups (66 ounces or 2000 mL) a day — and eat a low-sodium diet. Ask your doctor if you need to reduce the amount of animal protein (like meat or milk) that you consume. It can help to talk with a doctor or dietitian about the best foods for you.

Doctors will want to monitor people who have had kidney stones to prevent new ones from forming. So you may need to get a 24-hour urine collection test and blood tests. Depending on the type of kidney stone someone has had, doctors can prescribe treatments or medications to reduce the levels of crystal-forming substances in the urine.

Kidney stones aren't usually a worry for most teens, though it's always a good idea to eat healthy foods and drink enough to avoid dehydration (especially if you play sports).

Reviewed by: Robert S. Mathias, MD
Date reviewed: May 2013