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Although much more common in adults, kidney stones are becoming increasingly more common in children. Our approach to kidney stones focuses on treatment as well as prevention of future kidney stone events.
Causes of kidney stones
While the cause of increasing kidney stones in children is unknown. Some children may have too much of a certain substance (such as calcium) within the urine that contributes to kidney stone formation. Some children may have too little of another substance (such as citrate) within the urine that helps prevent kidney stones. Rarely, there are underlying genetic disorders or diseases that contribute to kidney stone risk. Kidney stones often run in families. Other known risk factors for kidney stones include feeding through gastrostomy (stomach) tubes, immobilization, certain medications to treat seizures, dehydration, recurrent urinary tract infections, and diet.
Presentation of kidney stones
Stones in the kidney can sometimes cause blood in the urine or pain, but more often are found incidentally (when looking for another problem). Most stones in the ureter will pass on their own; sometimes, a medication can be given to help the stone pass. If the stone is causing too many symptoms or does not pass on its own, sometimes surgery is needed.
Evaluation for kidney stones
For children with suspected kidney stones, ultrasound of the kidneys and bladder is preferred to minimize radiation exposure. A low dose CT scan is sometimes required if more information is needed.
After a kidney stone is found, often urine studies and sometimes blood studies are ordered to determine a cause for the kidney stone. If the stone passes or is removed surgically, it can be tested to determine what it is made of.
Surgery for kidney stones
There are three main types of surgeries for kidney stones: shock wave therapy, ureteroscopy, and percutaneous nephrolithotomy.
- Shock wave lithotripsy uses special sound waves sent through the body. There are no incisions and the procedure is non-invasive, but it is performed with the child asleep under general anesthesia. This therapy is effective for stones in the kidney or upper ureter if they can be seen on plain x-rays, but is not as effective for multiple or large kidney stones.
- Ureteroscopy uses a small camera and a laser to break the stone, and special instruments are used to remove the stone. This surgery is performed under general anesthesia and most children go home the same day. Sometimes, a ureteral stent (a thin plastic tube) is placed at a separate anesthesic procedure before ureteroscopy to help open the ureter more. Other times, the stent is left in place after the operation for a few days to weeks to help the urine drain. Either way, the stent is temporary and needs to be removed.
- Percutaneous nephrolithotomy is a procedure where a camera is placed directly into the kidney through an incision in the back. Often, the child is brought to the hospital the day before the surgery to have a tube placed through the back into the kidney under anesthesia by radiology. This helps the surgeon get into the correct location of the kidney for the surgery. This surgery is best for very large kidney stones and often requires several nights in the hospital.
A ureteral stent is a thin, plastic tube which extends from the kidney into the bladder through the ureter. A stent may be placed for several reasons. Sometimes, a kidney is blocked and infected or too painful and the stent is placed to help relieve the blockage before the stone can be removed. Sometimes, the ureter is too small to allow the ureteroscope (small, thin camera) and a stent is placed to help open the ureter. After the surgery, sometimes a stent is placed to allow drainage of urine and prevent kidney blockage from stone fragments, blood clots, or swelling of the urinary track. These stents are removed either by a string left on the stent coming out of the urethra or with a small camera again under anesthesia. Stents can sometimes cause bladder irritation or blood in the urine.
Prevention of kidney stones
50% of children with a kidney stone will have a recurrence, so it is important to focus on causes and prevention of kidney stones as well. The most common finding in children with kidney stones is poor fluid intake. Diet and fluids are the first-line steps in helping to prevent kidney stones. Children with a history of kidney stones should drink more water than recommended for the general population. High salt diets can cause excess calcium in the urine and therefore limiting salt intake is important to help prevent kidney stones. Some fruits, such as lemons and limes, contain citrate, a substance which helps to prevent kidney stones.
Although most kidney stones are made of calcium, children should not limit their calcium intake because they need the calcium for healthy bone growth. Sometimes, additional causes are found on urine or blood studies, which may require other treatments, most commonly daily medications to help prevent kidney stones.