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Pediatric Kidney and Ureteral Stones (Nephrolithiasis)

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Summary

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.

Expanded Overview

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. 

Types

  • 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. 
  • 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.  
  • 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.
  • 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.

Causes

  • Dehydration — Urine becomes more concentrated because of a lack of water, making it easier for crystals to form. 
  • 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.

Symptoms

  • Blood in urine
  • Cloudy or bad-smelling urine
  • Fever and chills 
  • Frequent urge to urinate or inability to urinate 
  • Irritability 
  • 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
  • Imaging: ultrasound, abdominal x-ray or CT scan
  • Blood test
  • Urine test

Treatment

  • Ureteroscopy with laser litotripsy - 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.

Prevention

Once results from the stone analysis and any blood or urine tests are obtained, then the goal will be to prevent future stones.  A thorough history and physical exam will help identify any medical conditions, medications, or prior surgeries that increase your child’s risk of kidney stone formation. 
General measures recommended to decrease stone formation for most children include:

  • Avoid excessive protein intake
  • Decrease salt intake
  • Dietary changes
  • Drink plenty of water
  • Medication

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.

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