What Are Kidney Stones in Infants and Children?
In kidney stone disease, or nephrolithiasis, stones (calculi) are present in the urinary tract. A kidney stone is formed when normally occurring mineral residue sticks together, making a larger solid piece of material. This is more likely to happen if you do not drink enough fluids.
Kidney stones may form quickly or slowly over time. They can cause sudden and severe pain.
Types of Kidney Stones
The four main types of kidney stones are:
- Calcium stones - the most common type of kidney stones.
- Cystine stones - resulting from a genetic disorder where cystine leaks through the kidneys into the urine.
- Uric acid stones - which form when the urine has too much uric acid in it. A diet rich in animal proteins may contribute to this kind of stone.
- Struvite stones - which form when someone has frequent urinary tract infections.
What Causes Kidney Stones to Form?
Low urine volume:
Low urine volume happens when a child does not drink enough fluids. This causes the urine to become concentrated and dark in color. Increasing fluid intake will dilute the urine and decrease the chance of stone formation.
The most common kidney stones are made from calcium. Calcium stones are usually caused by the way kidneys process salt in your diet. Some people pass larger levels of calcium into their urine when they eat a high-sodium diet. This can occur when eating a lot of processed and fast food or using too much table salt. The best way to decrease calcium stones is to reduce sodium in your diet. Your doctor or dietitian can give you specific guidelines to help reduce your sodium intake.
Some medications may cause low urinary citrate. Urinary citrate, a natural substance in the urine, protects against kidney stone formation. Some types of calcium stones are more likely to form in urine that is low in citrate. Your doctor may prescribe potassium citrate. You will be encouraged to eat a lot of vegetables and fruits, especially citric fruits, to make your urine richer in citrate.
Medical conditions that can cause urinary stones:
Hyperparathyroidism can cause too much calcium to be pulled from bones, leading to high calcium in blood and urine.
Cystinuria is an inherited genetic disorder where there is too much of the amino acid cysteine in the urine that can lead to cysteine stones.
Hyperoxaluria is where the liver makes too much oxalate, leading to kidney stones made from oxalate.
Hypercalciuria means the urine has a very high level of calcium. As discussed above, this can be due to various factors such as genetic predisposition, high sodium intake and / or medications.
- High salt in the diet can cause hypercalciuria.
- Some medications can cause hypercalciuria.
- Hypercalciuria is the most common genetic cause of kidney stones.
- Hypocitraturia means there are low levels of citrate in the urine. Low citrate can be related to diet or medicine.
- When citrate is low in the urine, calcium and uric acid kidney stones can form.
- Citrate helps remove extra calcium in the urine and can help prevent calcium crystals from forming kidney stones.
- This condition can be corrected with medications and changes in your diet.
Bowel or gastrointestinal conditions:
- In conditions that cause chronic diarrhea, such as Crohn’s disease or ulcerative colitis, kidney stones are more likely to form due to excessive fluid loss. Pay close attention to fluid intake if your child has these conditions.
- Some gastrointestinal diseases or surgeries, such as gastric bypass surgery or inflammatory bowel disease, can cause the intestines to absorb more oxalate from foods and form calcium oxalate stones.
Risk Factors for Kidney Stones
Factors that place a child at increased risk for developing kidney stones are:
- Family history of stones
- Decreased water intake or long periods of dehydration
- Repeated urinary tract infection
- Diet high in sodium and / or protein
- Decreased activity level
- Defects in the urinary tract
- Use of certain medications
How are Kidney Stones Diagnosed?
Kidney stones are often diagnosed in the Emergency Department, when children come in with severe belly or side pain. The following may be used to diagnose and locate stones:
- Medical history
- Physical examination
- Renal ultrasound: the most common radiologic test used to diagnose a urinary tract stone. The technician slides a hand-held device (transducer) across the child’s skin. This is a painless test using sound waves to take pictures of the kidneys, ureters and bladder. The images created may show the location of the stone(s).
- CT scan: the child lies flat on a bed that slides into a doughnut-shaped device. 3D pictures help to determine the location of the kidney stone.
- Kidney, ureter, bladder (KUB) X-ray: A quick, simple X-ray takes a picture of the child’s abdomen, which identifies some types of kidney stones.
Signs and Symptoms of kidney stones
Common symptoms of kidney stones include:
- Pain with urination
- Blood in the urine
- Frequent and persistent urinary tract infection
- Urinary urgency and / or frequency
- Nausea and vomiting
- Sudden, severe pain
- Pain in the belly, genitals or groin
Reasons to come to the Emergency Department for evaluation:
- Unmanageable pain
- Unable to keep down fluids
How are kidney stones treated?
The treatment for kidney stones depends on the size, what it is made of, and whether they are causing symptoms or blocking the urinary tract. Small stones will likely pass on their own without treatment, but will often require pain control and encouragement to drink a lot of extra fluids to help the stone pass. Larger stones or ones that block the urine flow may require surgery or hospitalization.
Extracorporeal shock wave lithotripsy (ESWL) uses focused acoustic shock waves to crush kidney stones. The smaller pieces can travel through the urinary tract more easily and eventually pass through the body. ESWL is done under anesthesia and usually takes about 45 minutes. No incision is needed.
Your child may need a ureteral stent if they have a blockage or narrowing of the ureter. The ureter is a slim, muscular tube that conducts urine from the kidney to the bladder. A ureteral stent is a soft, hollow tube that is placed temporarily in the ureter to hold it open. General anesthesia is used for this procedure. With the stent in place, the child may move around normally but should not do any strenuous activities.
This is a surgical procedure for removing medium to large stones from the kidney. It is done using general anesthesia. First, a tube is inserted into the kidney through an incision in the child’s back. Then, with the help of a very thin, fiberoptic instrument called a nephroscope, the doctor locates and removes the stone. This procedure may be combined with laser treatments to break up large stones for easier removal and with nephrostomy tube placement.
A nephrostomy tube is a small, flexible tube that is surgically inserted through the skin into the kidney to drain urine. The urine collects in a bag outside the body. This procedure may be needed to prevent kidney damage and infection if a kidney stone is blocking normal urine drainage, or temporarily after a large stone is removed. Nephrostomy tubes are placed by specialists, using general anesthesia. The procedure takes about an hour. Once the blockage has been relieved, the tube can be removed.
Kidney stones can cause severe pain as they travel from the kidney into the ureter, the narrow tube that drains the urine from the kidneys into the bladder. This pain, called renal colic, may cause nausea and vomiting. You can give your child Tylenol as directed for pain. Contact your doctor if your child does not get relief from the Tylenol.
How are kidney stones prevented?
The most important way to prevent kidney stones from forming is drinking a lot of fluids. This keeps the urine dilute and stones are less likely to form. Your child's doctor will also order a 24-hour urine collection that a special lab will evaluate to see what kind of stones their body is making. From that evaluation, the doctor can decide what medications or treatments your child may need to help kidney stones from forming.