CC, born with a single functional kidney, was referred to CHOP at 1 year of age with an obstruction in his ureter. He underwent robotic surgery to repair the obstruction, and a stent was placed to help maintain patency of the repaired ureter and minimize leakage during healing. Shortly thereafter, he developed multiple kidney stones in the area of the stent. He had a second surgery to remove the stones and was referred to Nephrology. The removed stones were analyzed and found to be 90% calcium phosphate and 10% calcium oxalate. Multiple urinalyses showed a high urinary concentrate of calcium, and CC was put on chlorothiazide to decrease his chance of developing urolithiasis in the future. He continued to be followed closely by his nephrologist, who advised drinking more fluids, and increased CC’s dose of chlorothiazide in response to continued high calcium-to-creatinine ratios—3.5 times normal. CC, now 7 years old, has remained stone-free and continues to have a normal functioning single kidney.
Discussion: One in 750 people are born with a single kidney, and 10% to 20% of people will develop a kidney stone during their lifetime. While for most kidney stone patients, a stone is a painful inconvenience, for those with one kidney, prompt recognition of urolithiasis is critical to prevent irreversible kidney damage or even kidney failure.
CC received follow-up care with Nephrology initially every 3 months for blood and urine tests and renal ultrasound. He is now seen every 6 months. As fluid intake is a critical component of stone prevention by effectively reducing the concentration of lithogenic factors, including calcium, oxalate, uric acid, and cysteine, we recommended CC drink an amount at least equal to calculated maintenance rates for his size plus 50%. Because he had very alkaline urine, which could predispose him to calcium phosphate stones (instead of the more common calcium oxalate stones), we advised giving him cranberry juice, which may have mildly acidified his urine and reduced the chance of forming new stones. We advised CC consume the recommended daily allowance for age of calcium to promote normal bone health and development.
Lifestyle changes are the suspected culprits in the 5-fold increase in pediatric kidney stones over the last decade. For otherwise healthy patients, the best predictor of kidney stones is a careful family history. Those with a family history of kidney stones are at 2.5 times greater risk of developing stones. Other conditions and medications that can increase risk are shown below.
Predisposition to Kidney Stones
These conditions and medications signal an increased chance a child may develop a kidney stone:
- Family history of kidney stones
- Frequent urinary tract infections
- Fracture history
- Seizure disorders
- Ketogenic diet
- Cystic fibrosis
- Spina bifida
- Inflammatory bowel disease
When urinary calculi develop during childhood, the risk of lifelong stone formation is significant, with approximately 20% having recurrences within 10 years. Children with an identifiable metabolic abnormality also need to be followed closely as they have an up to 5-fold increased risk of recurrence compared with children without metabolic disorders. Given the high risk of recurrences in children with idiopathic hypercalciuria and hypocitraturia and the importance of excluding rare but treatable conditions such as primary hyperoxaluria and cystinuria, a comprehensive metabolic evaluation is indicated in all children.
CC’s medical history makes him a perfect candidate for treatment in CHOP’s multidisciplinary Pediatric Stone Center, where specialists from Surgery, Urology and Nephrology deliver care in concert for complex patients. The center makes visits easier for families that no longer need to schedule separate appointments with those specialists to obtain the full range of treatment options. During appointments, the child can also see a nutritionist to get advice on changes in diet that can help prevent future stones.
The Pediatric Stone Center was created to treat medically complex patients, such as those who have spina bifida or other chronic conditions that restrict movement, and patients without underlying conditions but who have suffered from recurring kidney stones.
To help primary care pedestrians know when referral to specialists is appropriate, CHOP has posted a Pathway for the Outpatient Evaluation/Treatment of the Child with Urolithiasis. This clinical template outlines guidelines for kidney stone patients, including blood, urine, and imaging tests.
References and Suggested Readings
Copelovitch L. Urolithiasis in children: medical approach. Pediatr Clin North Am. 2012;59(4):881-896.
VanDervoort K, Wiesen J, Frank R, et al. Urolithiasis in pediatric patients: a single center study of incidence, clinical presentation and outcome. J Urol. 2007;177(6):2300-2305.
Pietrow PK, Pope JC IV, Adams MC, et al. Clinical outcome of pediatric stone disease. J Urol. 2002;167:670-673.
Diamond DA, Menon M, Lee PH, et al. Etiological factors in pediatric stone recurrence. J Urol. 1989;142(2):606-608.
To make a referral to or learn more about Nephrology, the Pediatric Stone Center and the Hypertension and Vascular Evaluation (HAVE) Program at CHOP, call 215-590-2449.