Pediatric Kidney Stones
What Are Kidney Stones?
A kidney stone is a small, hard deposit of mineral and acid salts that forms within the urinary tract. Some kidney stones are very small (about the size of a grain of sand), while others grow larger.
There are several different types of kidney stones, categorized by the type of mineral or acid salt they contain. The most common type is calcium oxalate, which accounts for 80 percent of kidney stones. Other types are: uric acid, struvite, calcium phosphate, and cysteine stones. It is important to identify and properly treat kidney stones, because they can obstruct the flow and drainage of urine.
Risk Factors for Developing Kidney Stones
If your child does not drink enough fluid, his/her urine can become concentrated which increases the chance for crystals to form.
A diet that is very high in protein, salt, fructose, or oxalate-rich foods (including leafy green vegetables, tea, or chocolate) can contribute to kidney stones. Additionally, up to 6 percent of children on ketogenic diets, for other medical reasons, will develop a kidney stone.
Children have a greater chance of developing stones if they have a parent or sibling who has also had a kidney stone.
Urinary Tract Obstruction
An obstruction in the urinary tract prevents urine from flowing properly and emptying from the bladder, which can result in kidney stones.
About 15 percent of children who have had a bladder augmentation (enlargement) procedure will develop a bladder stone.
Children with a disorder related to the muscles and nerves in the urinary tract are at an increased risk for stones due to urinary stasis.
Teenagers are more likely to develop stones than younger children, and girls are affected more often than boys.
Underlying Metabolic Disorder
Metabolic disorders like hypertension and diabetes often times are associated with abdominal obesity and insulin resistance. The insulin resistance can lead to an increased risk of kidney stone formation.
Symptoms of Kidney Stones
Symptoms can vary, especially in children. Typical symptoms include flank pain, nausea, vomiting, abdominal pain, groin pain, blood in the urine, pain with urination, or urinary frequency.
However, sometimes children with stones do not have any symptoms at all. Some children may only complain of non-specific abdominal pain, or they might see small or large amounts of blood in the urine, without having pain elsewhere.
How Are Kidney Stones Diagnosed?
Your child's urologist will conduct a physical exam, medical history evaluation, and a urinalysis to help determine if kidney stones are present. Depending on the size, location, and number of stones, the urologist will determine which imaging study is necessary. Imaging studies that are helpful to diagnose kidney stones include: X-ray, renal ultrasound (RUS), and abdominal/pelvic CT scan.
We may ask your child to ‘strain’ his urine with a special filter so we can send the stone for testing, if necessary, to determine the type of stone.
Treatment Options for Kidney Stones
We can treat stones in several ways, depending on their size, location, number and composition. Based on your child's specific needs, the urologist will recommend the most appropriate and effective treatment.
Most small stones can pass on their own, and do not require surgery. Your urologist may recommend medication:
- NSAIDs (Motrin, Advil, Toradol) for pain relief
- Tamsulosin (Flomax) relaxes ureteral smooth muscle, which helps the stones pass.
Surgery may be necessary if your child experiences any of the following:
- Stone is too large to pass on its own
- Stone blocks the flow of urine, which could cause infection or impaired renal function
- Stone causes ongoing urinary tract infections
- Stone has grown larger than previously seen on imaging
- Pain and symptoms are uncontrolled
- Persistent hydronephrosis (swelling of the kidney)
- Extracorporeal Shock Wave Lithotripsy (ESWL): Shock wave lithotripsy, ultrasonic energy or “shock waves” are used to break a larger stone into tiny stones that can pass more easily and naturally. This procedure is effective for stones in the kidney or upper ureter, and it is the least-invasive surgical option.
- Ureteroscopy: A long, thin scope is inserted through the urethra, and up into the ureter, to break up the stone using a surgical laser. The stones are removed with a small basket device that is deployed through the scope. A small tube (stent) may be left in for couple of days to promote healing and prevent blockage. This surgical option is appropriate if the child has already had an unsuccessful ESWL procedure, if the stones are hard, or if the stones have moved into the lower part of the ureter.
- Percutaneous nephrolithotomy (PCNL): During this surgical procedure, the kidney is directly accessed via a skin puncture. It is typically used to treat large-volume kidney stones (greater than 2 centimeters), staghorn stones (stones that take up a large portion of the kidney), or stones that are very difficult to access with ESWL or ureteroscopy.
After Treatment or Surgery
A follow-up renal ultrasound (RUS) or X-ray will usually be performed to ensure the stone is gone and the treatment was successful.
If your child has a stone, there is a 50 percent chance of having another stone within the next 5 years. To help us determine what caused the kidney stone, we may get some bloodwork and ask your child to collect urine for 24 hours to measure urine volume and levels of acidity, calcium, sodium, uric acid, oxalate, citrate, and creatinine. We will usually order these tests a few weeks after the symptoms and acute phase have resolved, ideally when the child is stone free. This is done to rule out any underlying metabolic disorder that may be contributing to stone formation.
Preventing Kidney Stones
There are ways to help your children avoid developing kidney stones. Make sure they drink plenty of water, and limit their intake of meat, salt, and foods that are high in oxalate. We may also recommend supplementing citrate in your child's diet to help prevent stones. Citrate is found in certain beverages such as Crystal Light, citrus fruits/juices, and it may also be prescribed for your child in pill form. Your urologist will discuss these options and recommendations with you.