Childen's Hospital Boston  300 Longwood Avenue
Boston, MA 02115
(617) 355-6000
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My Child Has:
Kidney Stone Disease
Programs that treat this condition
 Kidney Stone Center    Center for General Pediatric Urology  
What is stone disease?
Stone disease describes a condition in which chemicals in the urine crystallize into "stones" in the urinary tract. These stones can cause pain by creating an obstruction of the drainage of the urine. There are many different kinds of urinary tract stones, with calcium, oxalate, uric acid, and phosphate being the most common components.

Stones may cause problems anywhere in the urinary tract, from the kidney to the ureter and into the bladder. Most of the time, stones are found in the kidney or ureter.

Urinary tract
Click image to enlarge
How common is stone disease?
Stones are not common in children, but the incidence of stones in children does seem to be increasing. There are many minimally invasive methods for removing kidney stones, but few were originally designed for children.
What causes stone disease?
Stones form because there is too much of the ingredients of the stone and not enough water in the urine. This can occur either because there is an abnormally high amount of stone-forming material in the urine, or the urine is too concentrated because of dehydration.

In children, stone disease is less common than it is in adults. Some children who form urinary stones have an underlying abnormality or the urinary tract. These can include obstructions of the kidney and ureter, or diseases such as spina bifida. Many other children with stones have normal urinary tract anatomy.

What are the symptoms of stone disease?
The most common symptoms of stone disease include pain in the abdomen, flank (side), back, or groin, blood in the urine (hematuria), frequent urination, fever, or nausea and/or vomiting.
How is stone disease diagnosed?
Stone disease is diagnosed by imaging the urinary tract with x-rays, ultrasound, or CT scan. These studies may be ordered because your child is experiencing some of the symptoms described above. In other children, the stones may be seen on x-rays or other studies done for other reasons.
How is stone disease treated?
Your child's doctors will make treatment recommendations based on the size, location, number, and composition of your child's stone(s). In many cases, stones can be passed spontaneously without any surgical treatment - children can pass stones that are relatively large as compared to adults. In many cases your child's doctors will prescribe certain medications that have been shown to increase the chance of a stone passing spontaneously.

At other times, however, it is necessary to remove the stones; this decision is based on the child's condition and symptoms. It also may be appropriate to remove a stone that is growing so that it may be removed more easily, rather than waiting until it is very large.

The usual methods to remove a kidney stone in children include extracorporeal shock wave lithotripsy (ESWL), percutaneous nephrolithotomy (PCNL), ureteroscopy, or open stone surgery. The choice of technique depends upon the location, size and type of stone, as well as the child's medical condition and anatomy. All methods are possible in children.

ESWL

ESWL uses a special machine (the "lithotripter") to send shock waves through the skin into the patient's body and fragment the stone, and is the least invasive treatment for stones. The lithotripter focuses these shock waves at the precise point where the stone is located, which breaks up the stone. This is like focusing sunlight through a magnifying lens to create enough heat to burn. If you place your hand in the beam close to the lens it will not even feel warm as the light rays are not focused, but at the point where they are focused, they can burn paper.

The shock waves are focused so that they are intense at the position of the stone, but are more spread out at the level of the skin and therefore do not do any damage to the skin or internal organs. The positions of the stone and shock waves are controlled using ultrasound or X-ray guidance. Many shock waves are applied slowly, often several thousand, over about 20 minutes.

In older children, sedation can be used to control discomfort, but in small children, general anesthesia is used. The stone is fragmented and the pieces will pass over the following days. It may take up to 3 months for all fragments to pass, and this depends upon the position of the stone.

The overall success rate of ESWL is about 85%. Stones in the lower pole of the kidney are less likely to pass. Very hard stones such as those made of cystine or certain kinds of calcium stones, may not fragment very well.

URETEROSCOPY

This is a technique that uses a small scope passed up through the urethra into the child's bladder, and from there up into one or both ureters and kidneys. The stone can be seen using digital cameras attached to the scope, and the stone can be removed with a variety of special instruments designed to capture the stone. In other cases, a laser fiber is passed through the scope and the stone is fragmented into many tiny pieces.

Ureteroscopy is done under general anesthesia. Sometimes after ureteroscopy, a small flexible tube called a stent is left in the ureter to allow urine to drain from the kidney into the bladder. This stent may also help the stone fragments pass. Stents may be removed after a few days or weeks, either in the operating room or in the clinic.

The success rate of ureteroscopy is very high, upwards of 95%. Success rates are lower for large stones which may require multiple treatments, and for systems with difficult anatomy that makes it difficult to get the scope up to the stone.

PCNL

Percutaneous nephrolithotomy (PCNL) is a technique in which a needle is used to puncture the kidney under ultrasound or X-ray guidance and an instrument is passed into the kidney to allow direct examination, fragmentation and removal of a stone. This technique requires the patient to be completely asleep. A kidney drainage tube is usually left in place for 2 to 4 days.

PCNL is particularly useful in a patient with a hard stone that might not fragment with ESWL or in whom the anatomy of the kidney is not normal. In those children, fragmented stones may not pass effectively. If a stone has created a serious obstruction, a kidney drainage tube (nephrostomy) may have already been placed and this may be used to remove the stone. Stones may be removed using this technique all the way to the bladder.

In small children, the size of the tube used for access to the kidney must be adapted to the child's size. A special, small percutaneous access sheath has been developed here to permit access to the kidney for stone removal in small children. This system is very useful for small and moderate stones, but less so for large stones (>2.0 cm). Other techniques used involve obtaining access with a variety of methods. Most involve some sort of kidney puncture and dilation of the tract to permit endoscopic treatment.

OPEN STONE SURGERY

Years ago, almost all stones required open surgery for removal, and these operations comprised a major aspect of every urologist's practice. With advances in technology, however, most stones can now be managed with one of the less invasive approaches outlined above. Open stone surgery is now rarely done, but is still needed occasionally in specific patients with unusual anatomy or other specific situations.

Is there a chance that kidney stones will develop again?
There is a very high recurrence rate of kidney stones. Understanding the cause(s) of the kidney stone helps to determine appropriate medical treatment for prevention of recurrence.
What is the best way to prevent recurrence?
Effective prevention depends upon the type of stone and identifying risk factors for stone formation. Risk factors may be identified through a metabolic evaluation. At Children's, the metabolic evaluation is performed in consultation with a pediatric nephrologist, a pediatrician with advanced training in kidney diseases.

The metabolic evaluation includes:

  • detailed medical history
  • review of current prescribed and over the counter medications
  • detailed diet and fluid intake history
  • physical exam
Several tests are also performed including:
  • Analysis of urine - to assess for factors that contribute to stone formation, such as increased levels of calcium in the urine

  • Blood tests - to look for other risk factors

  • Chemical analysis of the stone (once it is passed or removed) - to identify the type of stone. This can provide important clues about why it formed.

  • Evaluation for inherited disorders - to look at risk factors. Several rare inherited disorders can lead to kidney stones.
The nephrologist analyzes the results from the above tests and determines the child's risk factors for stone disease.

Treatment plan
All patients are prescribed high fluid intake and a low-salt diet to reduce kidney stone recurrence. The nephrologist may prescribe medications to help reduce the formation of kidney stones. Specific treatment will be created for patients who are found to have an inherited disorder that leads to kidney stones.

Addressing high levels of calcium in the urine
The most common kidney stone is caused by too much calcium in the urine. This is often seen in families with multiple members with kidney stones. Medication can be prescribed which lowers the levels of calcium in the urine, helps calcium-forming crystals dissolve better in the urine.

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