Kidney Stones

A kidney stone is a solid mass made up of tiny crystals. One or more stones can be in the kidney or ureters (tubes that propel urine from the kidneys to the urinary bladder) at the same time. In recent years the incidence of pediatric kidney stone cases has dramatically increased. This is most notable in the adolescent population and in the southeastern United States.

Patients can be seen by Texas Children's experts in Urology.

Causes & Risk Factors

Kidney stone disease in the pediatric population has genetic, anatomic, metabolic, and dietary causes.When the concentration of certain chemicals in the urine become too high or too low, spontaneous formation of stone crystals can occur.

Children with certain anomalies of the urinary tract, urinary tract infections, or a family history of kidney stones are at a higher risk of developing urolithiasis. Children that are dehydrated are also at an increased risk of developing stones.

Children with stones usually present with pain in their abdomen or side. Other symptoms include blood in the urine, nausea, vomiting, urinary frequency, pain during urination and reduced urinary volume.  Stones can present anywhere in the urinary tract, from the kidneys down to the urethra (the tube that connects the urinary bladder to the genitals for the removal of fluids from the body).

There are numerous types of stones that a child can have.

-Calcium stones: These are the most common type of stone formed, accounting for over 80% of all pediatric stones. Calcium stones are caused by increased blood and urinary levels of calcium and are often associated with diets rich in sodium and carbohydrates.

-Struvite stones: These are stones associated with a urinary tract infection (UTI). The UTI affects the chemical balance of the urine and allows bacteria in the urinary tract to grow. This type of bacteria causes the stones to form.

-Uric acid stones:  These stones account for 10% of pediatric stones and are caused by increased levels of uric acid. Genetics play a role in the development of uric acid stones and are more common in boys.

-Cystine stones: Cystine is an amino acid in protein. Some children inherit a rare condition that results in increased amounts of cystine in the urine that can lead to these kinds of stones.

Diagnosis & Tests

Diagnosis of renal stone disease involves taking a medical history, physical exam, laboratory evaluation and imaging tests. The types of imaging used in diagnosing stones are ultrasounds, abdominal x-rays and CT (computerized tomography) scans. If the child is able to pass the stone, a stone analysis would be done to evaluate the type of stone present.

Treatment & Care

Treatment depends on the age of the child, the size and type of stone, the underlying cause, the presence of urinary infection and whether the stone recurs. Stones smaller than 4mm in diameter often pass spontaneously, but larger stones often require intervention.

At the time the stone is detected, your doctor will prescribe pain relievers. If the child fails to pass the stone surgical intervention may need to be performed. There are 4 methods most commonly used to break-up, remove or bypass kidney stones.

-Shock Wave Lithotripsy: This method uses a machine to break the stone into tiny particles that can pass naturally. Multiple treatments may be needed to get rid of the entire stone burden.

-Percutaneous nephrostolithotomy (PCN):This technique involves going through the skin over the kidney to remove the stone. This is procedure utilized for large stones.

-Ureteroscopic stone removal: In this procedure, an instrument is placed through the urethra and bladder to the level of the stone, and the stone is either removed with a basket or is broken up with a laser so the fragments can pass. A small stent (a small, mesh tube) may be left in the ureter afterwards to prevent blockage.

-Laparoscopic or Open Surgery: Both surgeries require general anesthesia and manual removal of the stone.

Living & Managing

Children with stones will often need to have their urine sent for a 24-hour urine collection. The results of this collection will guide medical recommendations to prevent future stone formation. Dietary changes may be required and water intake should be increased for most patients. After the stone is sent for analysis and the type of stone is determined some children might be treated through drugs. 

References & Sources

Baskin, Laurence and Barry Kogan, John Duckett. Handbook of Pediatric Urology. Philadelphia: Lippincott-Raven; 1997.

Surgical Managament of Pediatric Stone Disease. Campbell-Walsh Urology.  Wein, Kavoussi, Novick, Partin, Peters. 10^th edition, vol. 1. 3667-3684.