What Are Kidney Stones?
Kidney stones are small, solid masses that can form in the urinary tract. They happen when salts and minerals in urine (pee) get extra concentrated and then become crystals. Over a few weeks or months, the crystals can build up and become stones.
Kidney stones range in size from a fraction of an inch to several inches. Small kidney stones (0.2 inches or less than 5 mm) can pass through the urinary tract and out of the body with little or no pain. But larger stones can be quite painful, block the flow of pee, and cause blood in the urine and other symptoms.
Who Gets Kidney Stones?
Kidney stones (also called calculi or nephrolithiasis) mostly affect adults. But but kids and teens can get them. There are different types of kidney stones with many different causes, and they affect boys more often than girls.
What Are the Signs & Symptoms of Kidney Stones?
Usually, kidney stones don't cause symptoms until they move around in the kidney or pass into the . Small stones might pass through the urinary tract and out of the body with no pain or complications.
Larger stones, though, may block the urinary tract and cause symptoms like:
- 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 pee (making it red or brown), called hematuria
- nausea and vomiting
- needing to pee often or urgently
- fever or chills
A stone that's too large to move can sometimes create a backup of pee, causing one or both kidneys to swell (this is called hydronephrosis). Hydronephrosis can cause pain in the side and back. If it's not treated, it may cause long-term kidney damage. Most kidney stones, though, don't cause permanent damage.
What Causes Kidney Stones?
Most kids who get kidney stones have a health condition that increases their risk for them. But others get them for no known reason.
Some types of kidney stones run in families, so having a relative with kidney stones can make a person more likely to get them. Kids who have had kidney stones before are more likely to get them again.
Other risk factors include:
- Dehydration. Not drinking enough fluids can make pee become extra-concentrated. This increases the chance of crystals forming.
- An unhealthy diet and lifestyle. Drinking lots of sugary, caffeinated, or sports drinks and eating a diet high in sodium (salt) can increase the risk of calcium stones. Obesity also can make kids more likely to get them.
- Urinary tract defects. A structural defect in the urinary tract can block the flow of pee and create an area where it collects in a tiny pool. When pee stops flowing, crystal-forming substances may settle together and form stones.
- Some medicines. Some prescription and over-the-counter medicines can increase the risk of kidney stones if taken in large doses.
- Metabolic disorders. Having a metabolic disorder (a problem in the way the body breaks down and uses food) can lead to concentrated levels of oxalate (a substance made in the body and found in some foods) or cystine in the urine.
- Cystinuria. This genetic condition causes too much cystine to pass from the kidneys into the pee, causing cystine stones.
- Other medical conditions. A number of diseases and conditions can increase the risk of kidney stones, including gout (a type of arthritis), other kidney diseases, conditions that affect the thyroid or parathyroid gland, and some urinary tract infections (UTIs).
What Are the Types of Kidney Stones?
The four major types of kidney stones are:
- Calcium stones: The most common kind of kidney stone, these develop when calcium in the pee combines with other substances to form crystals.
- Cystine stones: These are rare and form when there is too much cystine (an amino acid) in the urine.
- Uric acid stones: These form when there is too much uric acid in the urine. Uric acid can crystallize by itself or combine with calcium to form a stone.
- Struvite stones: Also called staghorn calculi because they can look like a stag's antlers, these are made of a mineral called struvite. Struvite stones almost always are due to an infection of the kidneys or urinary tract. They're more common in females, can grow rather large, and can be more harmful to the kidneys than other stones.
How Are Kidney Stones Diagnosed?
See a doctor as soon as possible if your child has:
- pain in the side
- blood in the pee
- any other symptoms of kidney stones
Go to an emergency clinic or hospital emergency room right away if your child has:
- pain along with nausea, vomiting, fever, or chills
- trouble peeing
The doctor will ask about the symptoms and how long they've been going on; your child's diet; things that could be causing dehydration; any family of kidney stones; and any history of diseases or conditions that affect the kidneys or urinary tract.
The doctor will do a physical exam and probably order blood tests, urine tests, or kidney function tests to look for kidney stones. Imaging tests (such as ultrasounds, X-rays, or CT scans) are often used to get a better look at the kidneys. If there is a stone, an imaging test can show its exact size and location, which will help doctors decide on the best treatment.
How Are Kidney Stones Treated?
Treatment depends on the type of kidney stones and their size. Some kids just need to drink a lot of water and take pain medicines to pass a kidney stone. Those with larger stones may need surgery or other treatments to help remove the stones.
To help pass a small stone, give your child plenty of water to drink and medicine to ease the pain. Often, over-the-counter medicines such as ibuprofen and acetaminophen are enough. But sometimes prescription pain medicines are needed.
The doctor might ask you to strain your child's pee for a few days to collect the passed kidney stones. Examining the stones can help the doctor decide if further treatment is needed.
Kidney stones that block the urinary tract or cause severe pain or dehydration may require a hospital visit. In the hospital, a child may be given (IV) fluids and pain medicine to help stones pass and treat or prevent dehydration.
Large stones rarely pass on their own. To get rid of large stones and stones that are damaging the kidneys, doctors might use:
- Extracorporeal shock-wave lithotripsy. This treatment uses sound or shock waves to break kidney stones into smaller pieces that can be passed out of the body in pee.
- Ureteroscopic stone removal. A ureteroscope is a small tube with a camera at the end. In this procedure, doctors give the patient anesthesia, then thread the tube into the urethra through to the bladder. The tube is then threaded to the ureter and into the kidney until the stone is found. The ureteroscope has special tools that can remove the stone from the urinary tract or break it into smaller pieces.
- Percutaneous nephrolithotomy. This is used for large stones in or near the kidneys. Doctors insert a tube called an into the kidney through a small surgical cut in the back to remove the stone. For large stones, an ultrasonic probe can deliver shock waves that break the stone into small pieces that are easier to remove. People often stay in the hospital for a couple of days after kidney stone surgery.
- In rare cases, a type of open surgery called nephrolithotomy is done to remove large stones. This involves making a cut in the side to reach the kidney. X-rays taken during this procedure help surgeons find the kidney stone. Then, it's removed and sent to a lab for testing.
What Else Should I Know?
Doctors will monitor kids who have had kidney stones to prevent new ones from forming. Your child's doctor might have you use a 24-hour urine collection test. This measures the volume of pee within a 24-hour period and checks the substances in it.
Depending on the type of kidney stone your child had, the doctor can prescribe treatments or medicines to reduce the levels of crystal-forming substances in the pee.
Can Kidney Stones Be Prevented?
It's not always possible to prevent some types of kidney stones. But drinking enough water to avoid dehydration is important. Pee that's almost clear is a sign that a person is getting enough liquids. Cutting back on salt and salty foods also helps lower the risk of kidney stones.
To help prevent new stones, all kids who've had kidney stones should:
- drink a lot of liquids throughout the day. This can mean anywhere from 3 cups a day (for infants) to 8 cups a day (for teens). Ask your doctor how much your child should drink.
- limit the salt and protein in their diet
- not drink soda, soft drinks, or sports drinks
If dietary changes don't prevent kidney stones, medicines are available to lower the levels of crystal-forming substances in the pee.