research summary

Urine, Plasma Oxalate in Children With Primary Hyperoxaluria Type 1

Leigh Precopio

Children with primary hyperoxaluria type 1 (PH1) have higher urinary oxalate excretion when compared with older patients with PH1, which may put them at higher risk of comorbid conditions such as kidney disease. 

Researchers conducted a retrospective, observational study that included 403 patients with PH1 from the Rare Kidney Stone PH Registry from 2003 to 2018. All participants were genetically confirmed to have PH1 and had at least two measurements of urine oxalate-to-creatine ratio (Uox:cr), 24-hour urine oxalate excretion normalized to body surface area (24-h Uox), or plasma oxalate concentration (Pox) before 18 years of age.

A total of 83 patients met inclusion criteria and were included in the study. Participants were divided into three groups based on genetic mutations, both before and after using pyridoxine (vitamin B6): homozygous g170R, heterozygous G170R, and non-g170R AGXT.

The results showed that Uox:cr declined rapidly during the first 5 years of life. Patients with the non-G170R variant had the highest values for all three measures, both before and after initiation of B6 supplements.

Prior to B6 initiation, Uox:CR was similar in patients with heterozygous G170R and homozygous G170R. After B6 initiation, individuals with homozygous G170R had the lowest 24-h Uox and Uox:cr values. Both urinary oxalate excretion and Pox decreased over time during childhood. No differences were observed for estimated glomerular filtration rate among the groups.

The researchers note that these measurements should account for a patient’s age, body size, kidney function, and genotype.

“Children with PH1 under 5 years old have relatively higher urinary oxalate excretion which may put them at greater risk for nephrocalcinosis and kidney failure than older pH1 patients,” the researchers concluded. “Those with homozygous G170R variants may have milder disease.”



Sas DJ, Mara K, Mehta RA, et al. Natural history of urine and plasma oxalate in children with primary hyperoxaluria type 1. Pediatr Nephrol. 2024;39(1):141-148. doi:10.1007/s00467-023-06074-x