From the Guidelines
Patients with primary type 1 hyperoxaluria typically exhibit significantly elevated urinary oxalate excretion, ranging from 1.5-3.0 mmol/1.73m²/day, as demonstrated in recent studies 1.
Diagnosis and Assessment
The diagnosis of primary hyperoxaluria type 1 (PH1) involves assessing urinary oxalate excretion, along with creatinine, by 24-hour urine collection, as recommended by recent clinical practice guidelines 1.
- The 24-hour urine collection is considered the gold standard for diagnosing PH1, as it accounts for diurnal variations in oxalate excretion.
- Urinary glycolate is also elevated in approximately 75% of PH1 patients, making it a useful diagnostic marker alongside oxalate levels.
- For accurate results, 24-hour urine collections should be acidified to pH <2.0 to prevent calcium oxalate crystallization during storage.
Monitoring and Treatment
Serial measurements of urinary oxalate excretion are valuable for monitoring treatment efficacy, with successful interventions (high fluid intake, pyridoxine therapy, or liver transplantation) showing gradual reduction in urinary oxalate excretion over time 1.
- High fluid intake is recommended to prevent the formation of calcium oxalate kidney stones, with a target urine volume of at least 2.5 liters per 24 hours.
- Pyridoxine supplementation is effective in lowering urinary oxalate excretion in a subgroup of patients with PH1, and is recommended for all patients suspected to have PH1 or with genetically proven PH1 1.
- The dosage of pyridoxine should not exceed 5 mg/kg, and patients should be monitored for pyridoxine responsiveness, defined as a >30% decrease in urinary oxalate excretion after at least 3 months of treatment.
From the Research
Study Results for Primary Type 1 Hyperoxaluria
- The study 2 mentions that urinary excretion of oxalate is strongly elevated in patients with primary hyperoxaluria, with values greater than 1 mmol/1.73 m(2) body surface area per day.
- However, none of the provided studies directly report 24-hour urine sample results for patients with primary type 1 hyperoxaluria.
- The study 3 reports on the long-term effects of orthophosphate and pyridoxine therapy in patients with primary hyperoxaluria, including reductions in urinary supersaturation with calcium oxalate and improvements in crystalluria scores.
- The study 4 discusses the treatment of primary hyperoxaluria type 1, including the use of pyridoxine, which can reduce urinary oxalate excretion in some patients, and the role of liver transplantation in restoring hepatic enzyme activity and preventing further oxalosis.
Urinary Oxalate Excretion
- The study 2 notes that urinary oxalate excretion is elevated in patients with primary hyperoxaluria, but does not provide specific 24-hour urine sample results.
- The study 5 reports on the efficacy of RNA interference therapeutics in reducing urinary oxalate excretion in patients with primary hyperoxaluria type 1.
- The study 4 discusses the importance of reducing urinary oxalate excretion in patients with primary hyperoxaluria type 1, and the role of pyridoxine and other treatments in achieving this goal.