At the Pediatric Kidney Stone Center here at Children’s Hospital of Philadelphia (CHOP), our integrated clinic brings together pediatric urologists, nephrologists, psychologists, genetic counselors, kidney (renal) dietitians, radiologists, nurses, child life specialists, advanced practice providers and research coordinators in one program to offer the best possible cystinuria care for your child.

What is cystinuria?

Cystinuria is a rare, inherited condition where your child’s kidneys can’t take certain amino acids back into their body. Because of this, cystine builds up in your child's urine, which causes kidney stones that come back even after treatment. This affects both children and adults and often begins in childhood or adolescence.

Causes of cystinuria

Cystinuria is caused by changes in the genes (most commonly SLC3A1 or SLC7A9) that move four amino acids (cysteine, lysine, arginine and ornithine) around in your child’s kidneys. It is usually inherited when your child gets one recessive gene from each parent (an autosomal recessive pattern). Because cysteine doesn’t dissolve well in liquid, having too much of it in your child's urine can lead to kidney stones, especially if their urine is very acidic or concentrated.

Signs and symptoms of cystinuria

Your child with cystinuria may experience:

• Kidney stones that start in childhood and keep returning
• Side or abdominal pain
• Nausea
• Vomiting
• Blood in their urine
• Occasionally feeling an urgent need to urinate
• Repeated urinary tract infections
• Chronic kidney disease
• Urine that shows the hexagon-shaped cystine crystals characteristic of cystinuria when viewed under a microscope.

Testing and diagnosis for cystinuria

Here at CHOP, we coordinate testing, imaging and counseling into a single-day appointment, so your family doesn't have to shuttle between clinics. We also combine results into a single treatment plan for your family’s ease.

We use a combination of family history, urine testing, imaging and genetics to help diagnose your child:

• Urinalysis & microscopy – We examine your child’s urine using a microscope to look for cystine crystals.
• 24-hour urine profile – This is a 24-hour urine test that allows us to measure the amount of your child’s urine, its pH balance, and the amounts of cystine and sodium to help guide kidney stone prevention.
• Stone analysis – Examining a stone after it passes or is removed with surgery allows us to determine if it is made of cystine.
• Genetic testing and counseling - Helps us confirm the diagnosis and give families useful information for screening.
• Imaging – We use ultrasound to assess your child’s symptoms and to monitor kidney stone formation. If we still need more information, we will also use a pediatric ultra-low-dose CT -- but only when necessary.

Treatment for cystinuria

Our approach to care focuses on what causes cystine stones—too much cystine and urine that’s too acidic—while working to reduce the need for procedures whenever possible.

Medical & nutrition therapy

• Hydration support - We help you and your child make a realistic plan for them to drink enough fluids each day, with tips for school, sports and reminders at home.
• Urine balance (alkalinization) - We use potassium citrate to keep your child’s urine at a healthy pH level, which helps cystine dissolve more easily.
• Nutrition guidance - Our kidney dietitians create personalized food and nutrition plans that include guidance about the right levels of sodium and protein for your child. Our goal is to lower their cystine levels while making sure they continue to grow and stay healthy.
• Medicines to bind cystine (when needed) - Some children who still have high cystine levels may take medicines like tiopronin or d-penicillamine. CHOP kidney specialists carefully monitor lab results, side effects and dosage using 24-hour urine tests.

Expert surgical care when stones need to be removed

• Child-sized options that spare their kidneys - Our team uses minimally invasive techniques, like ureteroscopy with laser treatment and mini-percutaneous nephrolithotomy (mini-PCNL), that are designed for children.
• Specialized pediatric team - Our experienced surgeons and anesthesiologists use child-focused pain plans, same-day recovery options and imaging with the lowest possible radiation.
• Comprehensive support before and after surgery - Our urologists, advanced practice providers, psychologists and child life specialists work closely together to prepare your child for surgery. Then our urologists, nephrologists, advanced practice providers and dietitians work as a team to help prevent new stones from forming after surgery.

Integrated support for your family

• Coordinated care - Our nurses and advanced practice providers help organize everything—from imaging and lab tests to prescriptions and school plans—so your child’s care runs smoothly.
• Whole-child services - Genetics, psychology and child life specialists are part of your care team to support your child’s medical and emotional needs.
• Quick help for painful stone episodes - We offer fast-track care options to manage pain and treatment quickly, and to help your family avoid long waits in urgent care or the ER.

Follow-up care

Follow-up care is an important part of keeping your child healthy and preventing new stones. Early on, visits usually happen every three to six months, then gradually become less frequent as your child meets their goals. 

At each visit, we check growth, blood pressure and urine pH. We conduct lab tests for medications and ultrasound imaging based on your child’s stone risk. You can expect us to perform 24-hour urine collections every six to 12 months.

We help your child build skills for home and school, including staying hydrated, monitoring their urine pH and knowing what to do if symptoms appear. Finally, when your child is ready, we provide a smooth transition to adult kidney stone specialists to continue their care.

Outlook for children with cystinuria

With regular prevention, prompt treatment when stones appear and guidance for families, most children with cystine stones can stay active and protect their kidney health. While the chance of stones coming back is higher than with other types of kidney stones, preventative care with our dedicated team of specialists can reduce emergency visits, procedures and missed school days.

Research

Families at CHOP can take part in cutting-edge research on pediatric kidney stones. Our work includes: 

• Precision diagnostics - Advanced urine testing and new ways to interpret 24-hour urine results, developed with the Center for Diagnostic Innovation here at CHOP.
• NIH-funded multicenter studies - We participate in national, NIH-funded studies that bring together multiple centers to better understand and treat childhood kidney stone disease.
• Microbiome and metabolome - Other projects explore the tiny bacteria and other microbes living in your body that help keep you healthy (microbiome) and the small chemicals your body makes as it uses food and energy, which can show how your body is working (metabolome). The goal is to find new markers and ways to prevent stones.
• Patient-centered trials – We test hydration support, imaging plans and digital tools to track your child’s symptoms at home.
• Biobanking & patient-reported outcomes (PROs) - These are optional programs that pair blood, urine, or tissue (bio samples) with family-reported data to help speed discoveries that help advance kidney care.