Tackling kidney stones: Q&A with Boston Children’s Kidney Stone Program co-directors

kidney-stones-in-childrenIn recent years, there has been a steep and steady increase in the incidence of kidney stones in the pediatric population. Based on this increase, Boston Children’s Hospital established a pediatric Kidney Stone Program in 2007 to help manage the influx.

Caleb Nelson, MD, MPHBartley Cilento, MD, MPH, and Michelle Baum, MD, program co-directors, discuss why kidney stones are becoming more common in children. 

How has your patient volume grown?

Dr. Nelson: A few years ago, we’d see a new patient about once a month. Now our team sees new cases every week. We have four Kidney Stone Clinics each month: two in Boston, one in Waltham and one in Weymouth. We also have a new location at our North Dartmouth satellite where we hold clinic regularly.

What do you think is causing this increase?

Dr. Nelson: There may be a number of reasons. Children are getting less physical activity, which is contributing to an increased incidence of obesity. Obese people are more likely to get stones, although both obese and non-obese children and adults can get them. We don’t know if obesity itself causes stones, or if obesity is just a marker for other factors that cause stones. Diet is a factor, as many children eat too much salt and highly processed foods and don’t drink enough water. Stones form when there’s too much of the stone-forming material and not enough water in the urine, so dehydration is a major contributor.

What are typical symptoms?

Dr. Cilento: Symptoms may vary from none (in the case of “silent stones”) to excruciating pain due to urinary obstruction. Most obstructing stones cause pain, nausea and vomiting. In older children, flank or back pain is also typical. In younger children, symptoms may be vague, and the child may not be able to pinpoint the location of his or her pain. For all children, gross or microscopic blood in the urine is a key indicator; any child with pain accompanied by blood in the urine should be evaluated.

What are the most common types of kidney stones in children?

Dr. Baum: The most common type of kidney stone in children is a calcium-based stone, either calcium oxalate or calcium phosphate. Struvite stones may be seen in children with chronic urinary tract infections or with urinary tract abnormalities and cystine stones are quite rare and represent a rare genetic disorder leading to kidney stones called cystinuria.

What are the treatment options for patients?

Dr. Cilento: Treatment is determined based on the size, location, number and composition of the stone(s). In many cases, they can be passed spontaneously without any surgical treatment, since children (unlike adults) can pass stones that are relatively large. Other times, it’s necessary to remove them.

The most common removal treatment is extracorporeal shock wave lithotripsy, which uses a noninvasive device to send shock waves through the skin and into the body to fragment the stone. Other endoscopic techniques to remove stones and stone fragments, such as ureteroscopy or percutaneous nephrolithotomy, are indicated based on stone size, position and number.

Dr. Baum: We also do a metabolic evaluation and take a urine sample to assess for factors that contribute to stone formation, such as increased levels of calcium in the urine. We perform blood tests to look for other risk factors.

Once the stone is passed or removed, we perform a chemical analysis to identify its type. This can provide important clues about why it formed. We perform 24-hour urine stone risk profiles to understand fully the risks for kidney stones, and we can use these profiles to follow the impact of our medical treatments and the reduction of risk as a result of treatment.

What’s the best way to prevent recurrence?

Dr. Baum: We prescribe individualized treatment plans for all our patients, including high fluid intake and a no added salt diet. Medications may be prescribed to help prevent crystals from forming in the urine and to help substances dissolve in the urine. After a child has his or her first stone and we complete our initial evaluation, we like to see the child twice a year. We check to see how much fluid the child is drinking, compared to our set goals; monitor symptoms; and do follow-up urine and blood tests. We check for the development of new stones via follow-up ultrasound, or, when indicated, low dose non-contrast CT.

In the near future, an important prophylactic component will be identifying a genetic cause of stone disease.

When should a child see a specialist?

Dr. Nelson: All children with proven or suspected kidney stones should be seen by urology and nephrology. This is a potentially life-long condition that needs thorough investigation to reduce risk of long-term sequelae.

Caleb Nelson, MD, MPH; Michelle Baum, MD; and Bartley Cilento, MD, MPH

Learn more about the Boston Children’s Kidney Stone Program.