A kidney stone is a hard deposit of mineral and acid crystals that sometimes forms inside a kidney. Most times, a child has no long-term effects after the stone passes from the body, carried out by urine. But kidney stones can cause extreme pain while they pass. Usually, the worst pain is felt after the stone enters the narrow tube (the ureter) that carries urine from each kidney to the bladder.
How does a kidney stone form? Think of building a snowball: you start with a small amount of snow that forms the snowball’s core. As you pack on more snow, it gradually changes from a loose handful of snowflakes to a tight sphere. This change lets more snow stick. Gradually, the snowball gets bigger.
That’s what happens when a kidney stone forms, except the building blocks are mineral and salt deposits. The kidneys are the body’s main blood-cleaning organs. They filter the mineral and salt deposits out of the blood as waste products. But when these deposits “snowball” in a kidney, they may eventually form a stone.
- Building up, but not flushing out: Many times, the building blocks of kidney stones are salt byproducts. The byproducts crystallize, stick together and harden because the child doesn’t drink enough. A child who is dehydrated for long periods is more at risk for developing a kidney stone.
- Runs in the family: A child (or adult) whose relatives had kidney stones is more likely to develop a kidney stone at some point.
- Medical condition: For some children, an abnormal condition in the urinary tract makes it easier for stones to form. The kidney or ureter may be obstructed. The child may have a urinary tract infection. Sometimes, a metabolic condition or disease, such as spina bifida, is the cause.
Kidney stones can pass naturally with good medical advice and attention. When there’s infection, severe pain or an obstruction, expert advice and care is needed to get rid of the stone.
Kidney stones can form in children of any age, even infants. Stones are becoming far more common in school-aged children and teens.
Extra Weight and Salt
“We don’t understand exactly why, but it is possible that this increase is linked to lifestyle factors, like more children becoming heavier and eating diets higher in salt,” says Edward M. Gong, MD, attending physician, Urology. “Excess salt intake means the kidneys may build up more salt as they do their job of filtering the blood.”
Sometimes, the stone blocks the flow of urine from the body. If this happens, waste products can build to harmful levels. This can create infection in the kidney or throughout the body.
If left untreated, infection can even lead to permanent kidney damage. “If we suspect any of these complications, we’ll take immediate steps to drain your child’s urine and treat any signs of infection,” says Dr. Gong. “We’ll also talk with you about when and how we’ll need to remove the stone.”
Preventing Stones, Keeping Kidneys Healthy
Even in children and teens, kidney stones tend to happen again. We’ll talk to you about what you can do to prevent other kidney stones from forming. Making sure your child drinks enough fluid is extremely important in kidney stone prevention.
Diagnosis & Treatment
The symptoms and treatment depend on where the stone is exactly and how big it is. Some kidney stones stay in the kidney without causing any symptoms.
Sometimes, a kidney stone is discovered when a child gets an abdominal scan for some other reason. When this happens, we may recommend watchful waiting — unless the stone is extremely large or begins causing pain.
Trouble typically starts when a stone moves from the kidney into the ureter. The pressure of urine backing up in the ureter or kidney creates intense pain. The pain stops when the pressure stops, either because the stone passed or was removed.
Here are key symptoms to watch for:
- Sharp pain: The pain is around the back and sides; it may be constant or come and go
- Nausea and vomiting
- Blood in the urine: When there’s blood in the urine, the child needs to be seen by a medical professional promptly, even if it’s just a small amount and even if the child has had kidney stones before
To help the child, we get the medical history, do an exam, get an image and test the urine.
- History and exam: We do a physical exam, and we take a careful history of the child and family. Does anyone in the family have gout, arthritis or chronic kidney disease? Has a relative had a kidney stone? Does the child have a urinary tract infection?
- Imaging: Seeing a picture of the inside of the abdomen is a must for diagnosing a kidney stone. To plan the most appropriate treatment for your child, we need to know as much as we can about the stone’s precise size and location.
- We nearly always start with an ultrasound because this gives us fairly detailed information without exposing your child to radiation. Patients at Lurie Children’s Hospital can receive ultrasounds 24 hours a day, seven days a week, unlike at many general hospitals.
- Occasionally, if we need to plan for surgery, we get a CT scan after the ultrasound. This tells us the stone’s exact size and location.
- Urine test: Typically, we order a urine culture to look for infection. Usually, we don’t need any blood tests to make the diagnosis, unless the child shows sign of widespread or serious infection.
Planning Your Treatment
A kidney stone four millimeters in size or smaller is likely to pass on its own, even in very young children. We might allow up to six weeks for this to happen, unless there is infection or persistent pain. A stone larger than five millimeters or so usually needs help getting out of the body. The child’s body size is a factor in how likely a stone is to pass on its own. We’ll base the treatment plan on what we know about the stone’s size, location and composition.
- Watchful waiting: If the stone is of a size that’s likely to pass on its own, we’ll recommend that the child drink lots of water, take pain medicine as needed and have a follow-up appointment after about two weeks. We’ll give you a strainer and tell you how you or the child should strain the urine — in hopes of collecting the stone. That way, we can analyze it and tell you how you may prevent new stones.
- Lithotripsy: This outpatient procedure isn’t invasive, but requires general anesthesia. We use high-energy shock waves to break the stone into small enough particles to pass through the urinary tract. Over the course of about an hour, we carefully direct up to 2,000 waves at the stone. After we break up the stone, the tiny pieces can take up to several weeks to pass. Their passing may be uncomfortable.
- Ureteroscopy: This outpatient procedure is minimally invasive. We insert a telescoping fiber-optic instrument through the child’s bladder via the urethra (the tube that carries urine out of the body). Once we reach the stone, we can either remove the stone using a small collection device at the end of the instrument or we can break up the stone with a laser beam that we shine through the instrument. If we break up the stone, the pieces can then pass on their own. To speed healing, we often insert a small tube or stent into the ureter. At Lurie Children’s, ureteroscopy is generally our preferred way to treat a kidney stone.
- Percutaneous nephrolithotomy: We use this laparoscopic surgery mostly for large stones of 1.5 centimeters or greater. We make a small incision in the child’s back above the kidney, then use imaging to help us guide a catheter to the stone. We can either remove the stone using a basket on the instrument or break up the stone into smaller pieces before removing it. There’s less bleeding and faster healing than with open-field surgery because the incision is smaller.
The Weeks Ahead
If we get to analyze any pieces of the stone, we can learn what the stone was made of. We look for information in the urine and blood, too. After two weeks or so, the child should be eating and drinking normally, recovered from the pain and any surgery and doing usual activities. After analyzing urine and blood samples, we’ll have information to share with you about what may have caused the stone and future prevention.
Health complications in adult life — such as chronic kidney disease, bone disease and hypertension — may follow after having kidney stones as a child. Kidney stone disease may harm kidney function.
Make an Appointment
Learn more about kidney stones in children by visiting the following doctor-recommended sites: