Pediatric Nephrolithiasis (Kidney and Ureteral Stones)
A kidney stone forms when substances in the urine become highly concentrated. The causes can include a blockage in the urinary tract, a genetic tendency, drinking too little water or eating too much salt, a bacterial infection in the urinary tract, or a condition that prohibits the body from effective digesting food.
Pediatric kidney stones vary in shape and size, from the size of a grain of sand to the size of a golf ball (in extreme cases). When these stones are larger than the urinary tube, they can get lodged in the urinary tract and cause intense pain.
Stones pass from the kidney to the ureter (the tiny tube that connects the kidney to the bladder). Some kidney stones are small enough to pass without being noticed. Others are larger than the tube and become stuck when trying to pass through. This leads to a urine backup in the kidney, ureter, bladder or the urethra (which takes urine from the bladder out of the body) – wherever the stone is stuck.
- Calcium stones — The most common type of kidney stone in children is made of calcium oxalate or calcium phosphate. Calcium in the diet does not increase the risk of this type of stone.
- Cystine stones — These are a side effect of a genetic disorder called cystinuria. The child’s kidneys leak large amounts of an amino acid called cysteine. Cysteine crystals can form stones.
- Struvite stones — These stones can form after an infection in the upper urinary tract. They develop suddenly and become large quickly. They often affect children whose urinary tracts did not develop normally.
- Uric acid stones — These stones form when a child’s urine contains too much uric acid, due to inherited conditions or diet. The body creates uric acid when it breaks down substances called purines, a natural chemical compound found in many foods and drinks.
There are many causes of kidney stones, but the most common reason is eating too much salt and not drinking enough water. In fact, the formation of a kidney stone is actually multiple small salt crystals sticking together and growing until it becomes a visible stone.
To describe how kidney stones form, ask your child to imagine sea water evaporating and leaving salt crystals behind. When these stones become large enough to become painful, they may even block the kidneys or the tubes (ureters) that carry urine.
Other causes may include:
- Medications - Certain medications, like diuretics (pills that help rid the body of water) or calcium-based antacids, can lead to kidney stones.
- Metabolic disorders - If the body doesn’t break down food properly, it can lead to concentrated levels of oxalate or cysteine in the urine.
- Other health conditions - This can be from genetic conditions that change the shape of the urinary tract, like cystic fibrosis and cystic kidney disease.
- Non-genetic conditions also play a role, such as repeated urinary tract infections, an inflamed bowel or gout (a type of arthritis).
- Sodium - A diet high in sodium adds extra minerals to the urine that can become kidney stones.
- Sugary foods and drinks - Ingesting too much fructose (sugar) correlates with increasing risk of developing a kidney stone. Fructose can be found in table sugar and high fructose corn syrup.
- Blood in urine
- Cloudy or bad-smelling urine
- Fever and chills
- Frequent urge to urinate or inability to urinate
- Nausea and vomiting
- Pain while urinating
- Sharp pains in the back, side, lower abdomen or groin
Tests and Diagnosis
- Analysis of kidney stones that have passed
- Blood test
- Imaging: ultrasound, abdominal x-ray or CT scan
- Urine test
Depending on the size and severity of your child’s kidney stone, we typically recommend this series of treatment options:
- Basic pain management if we think there is a chance the stone will pass on its own
- Changes in diet, especially increasing the amount of water your child drinks each day
- Ureteroscopy with laser lithotripsy - a procedure that allows the surgeon to see inside the bladder and ureter and then, by using a small laser, break up the stone into small pieces that can be passed during urination.
- Extra-corporeal shock wave lithotripsy (ESWL) - the use of high-energy sound waves to break up the stone into small pieces that can be passed during urination.
- Percutaneous nephrolithotomy - a surgical procure that requires a small incision into the kidney. A tube is inserted and the surgeon is able to locate and then remove the stone through the tube.
The procedures will be discussed in more detail at your clinic visit. Sometimes a temporary drainage stent needs to be placed before or after the surgery.
Stones may be prevented by:
- Increasing the amount of water your child drinks each day, especially in the warmer months.
- Reduce the amount of salts that may form stones. It turns out that one of the best ways to do this is to reduce the amount of table salt, also known as sodium chloride, that your child eats.
In addition, when certain substances we eat and drink pass through our urine, they can prevent salt crystals from sticking together to create kidney stones. Change the acidity of the urine (pH) and increase the amount of citrate in the urine by drinking lemonade or orange juice, which contain natural citric acid.
We can also reduce the risk of stones by avoiding oxalates, found in dark leafy vegetables such as kale, spinach and rhubarb, as well as in peanuts, chocolate and tea. Your child does not have to avoid these altogether, but it’s best not to consume them often or in large serving sizes.
Along with any relevant medical history, results from initial blood and urine tests will guide the pediatric urologists and nephrologists to recommend any additional testing or medications to prevent future stones.