Here at Children’s Hospital of Philadelphia (CHOP), care for primary hyperoxaluria (PH) is rooted in deep expertise and teamwork across multiple specialty departments. Our experts in the Division of Nephrology and the Division of Urology, along with nutrition, psychology and advanced practice providers, partner to deliver better outcomes for your family through innovative approaches to family-centered care. 

Our Pediatric Kidney Stone Center is experienced in diagnosing rare stone conditions like PH. Our kidney experts use information from the high volume of patients we care for to identify subtle signs early and help reduce long-term complications. Families come to CHOP from across the region, the country and around the world for the level of expertise and coordination we offer. 

What is primary hyperoxaluria?

Primary hyperoxaluria (PH) is a rare inherited (genetic) disorder in which your child's body makes too much of a waste product called oxalate that should normally be removed from their urine. 

Types of hyperoxaluria

There are three types of primary hyperoxaluria — PH1, PH2 and PH3 — each caused by a different genetic change that affects how oxalate gets processed in your child’s body.

• PH1 - The most common and often most serious form, caused by mutations in the AGXT gene
• PH2 - Caused by changes in the GRHPR gene, PH2 tends to show milder symptoms
• PH3 - Caused by changes in the HOGA1 gene and generally less severe

Here, we will focus on children living with primary hyperoxaluria type 1 (PH1), the most common type of primary hyperoxaluria.

In children with PH1, a change in a gene called AGXT prevents your child's liver from processing oxalate correctly. Too much oxalate can form hard crystals that can lead to kidney stones and damage the kidneys over time, possibly causing kidney failure if not treated.

What are the causes of primary hyperoxaluria?

PH1 is a genetic disorder where your child receives changes in two copies of the AGXT gene — one from each parent. Parents who each carry one of this genetic change do not usually have symptoms themselves, but their child can if both copies of the gene are affected. This is called an autosomal recessive pattern.

What are the signs and symptoms of primary hyperoxaluria?

Children with PH1 can develop symptoms at any age between infancy and adolescence, and symptoms can vary widely. Some common signs you may see include:

• Kidney stones that cause pain or block the flow of your child’s urine 
• Blood in your child's urine
• Pain when urinating or needing to pee often (urinary frequency)
• Bedwetting or changes in bathroom habits
• Declining kidney function
• Kidney failure

How do testing and diagnosis work for primary hyperoxaluria?

Your child’s CHOP care team will listen carefully about your child’s symptoms, review their medical history and work together to determine the appropriate tests, to help get the right diagnosis and care for your child as early as possible. 

Testing for PH1 typically involves:

• Blood and urine tests to measure oxalate and check kidney function
• Genetic testing to confirm the gene changes involved
• Imaging tests (like ultrasound) to look for kidney stones or damage
• Stone analysis, if your child has passed a kidney stone

At CHOP, specialists in pediatric nephrology and urology coordinate these tests, so your child gets the right evaluations at the right time. Genetic counselors and nutrition experts are part of the team to help families understand test results and how they may apply to future care and lifestyle needs.

What is the treatment for primary hyperoxaluria?

The primary goals in treating PH1 are to reduce oxalate production and buildup in your child’s urine, protect your child’s kidney function and manage any kidney stones. Your child’s CHOP care team will work together to create a treatment plan that addresses immediate stone issues and helps prevent new stones from forming. 

A treatment plan for PH1 may include:

High fluid intake - Encouraging your child to drink fluids throughout the day helps dilute urine and reduce stone formation.

Medications and supplements -

• Some medicines work by turning off specific genetic instructions in the liver that tell the body to make oxalate (RNA-targeted medicines). By blocking these instructions, medicines like lumasiran or nedosiran help your child’s body produce less oxalate and lower the risk of kidney stones.
• Medicines like citrate can prevent the growth of crystals in urine (crystallization inhibitors) and may be used to make it less likely to form stones.
• Supplements like vitamin B6 that are easily dissolved in water (pyridoxine) and don’t stay stored in the body for long can help reduce oxalate production in some PH1 patients.

Surgical and procedural care - When kidney stones form, our urologists may use minimally invasive procedures to remove the stones, help reduce pain and speed recovery. 

Kidney support and transplant - If PH1 leads to kidney failure, our team will discuss options with your family that include dialysis, kidney transplant, and in some cases, combined liver-kidney transplant that can help correct causes from the way your child’s body processes food and chemicals (metabolic causes) and restore kidney function.

Follow-up care for primary hyperoxaluria

PH1 is a lifelong condition that needs regular monitoring. Follow-up visits may include:

• Checking kidney function and oxalate levels
• Updating medication and fluid plans
• Monitoring imaging studies
• Nutrition counseling
• Tips to support school performance and emotional health

Outlook for children with primary hyperoxaluria

Every child is different, but early diagnosis and specialized care can make a meaningful difference. With new treatments like RNA-targeted therapies and careful long-term monitoring, many children with PH1 can have fewer stones, better kidney function and improved quality of life. CHOP experts work with families to plan care that evolves with your child as they grow.

Research

Because research is at the heart of CHOP’s mission, our Pediatric Kidney Stone Center has been designated as a frontier program. The elite frontier programs at CHOP conduct visionary research that translates to lifesaving treatment and cures, and they often offer answers not available anywhere else in the world. Our center brings together clinical care and advanced research, including multi-omics studies that aim to create new diagnostic tests — such as quicker urine tests that may one day transform personalized management of rare stone disease. 

Our researchers also collaborate with national networks like Pediatric Kidney Stone Care Improvement Network (PKIDS) to study outcomes and develop better ways to diagnose and treat stone diseases in children. 

We are driven to find life-changing solutions for children with PH1 and other complex kidney conditions, and we translate these discoveries into better care for your child and families everywhere.