Abstract: PO1999
Oxalate and Glycolate in Urine and Plasma Related to Kidney Function, Dialysis, or Transplantation in Patients with Primary Hyperoxaluria Type 1
Session Information
- Pediatric Nephrology: Genetics, Kidney Stones, Quality Improvement, and Case Reports
November 04, 2021 | Location: On-Demand, Virtual Only
Abstract Time: 10:00 AM - 12:00 PM
Category: Pediatric Nephrology
- 1700 Pediatric Nephrology
Authors
- Hoppe, Bernd, German Hyperoxaluria Center, Bonn, NRW, Germany
- Pick, Julia, Zentrum fur Kinderheilkunde der Universitat Bonn, Bonn, Nordrhein-Westfalen, Germany
- Martin Higueras, Cristina, German Hyperoxaluria Center, Bonn, NRW, Germany
Background
Primary hyperoxaluria type 1 (PH1) is characterized by endogenous oxalate overproduction in the liver, extremely elevated urinary oxalate excretion (Uox), thus recurrent urolithiasis and/or progressive nephrocalcinosis and chronic kidney disease (CKD). It also leads to early renal failure, especially problematic in the young patient (infantile oxalosis). Uox and glycolate (Uglyc) and plasma oxalate (Pox) and glycolate (Pglyc) are used as biochemical markers for diagnosis, treatment and follow up, but also as primary endpoints in studies.
Methods
We retrospectively analyzed these parameters in urine and plasma of 87 genetically confirmed PH1 patients over the last 15 years. All parameters were analyzed by ion-chromatography/mass spectrometry and in the same lab. Correlation and comparative analyses were performed within groups of different renal function (normal, CKD 1-5; n=48 patients), hemodialysis (HD; n=31), transplantation (Tx; n=32) and related to vitamin B6 medication.
Results
From normal kidney function to CKD3-4 Pox remained stable (median Pox 17 µmol/l), while Pglyc was more markedly elevated (median 90.12 µmol/l). Both were significantly higher in non-B6 versus B6 sensitive patients. Pox and Pglyc did not correlate with kidney function, except for Pox and CKD5. Highest Pox and Pglyc was found in HD (91 and 211 µmol/l, respectively), not related to B6. Uox and Uglyc remained stable at all CKD stages in B6 sensitive, but increased progressively in B6 unsensitive patients. Pox and Uox slowly declined post combined and sequential liver-kidney, but also in isolated kidney Tx, which was performed in adult B6-sensitive patients. In the contrary, PGlyc remained elevated post Tx.
Conclusion
Our findings are in many ways contradictory to previously published observations. Pox or Uox did not correlate to GFR. Pox was surprisingly low until HD and Uox increased until CKD3-4 in non-B6 sensitive patients. PGlyc remained elevated even years after transplantation, but no data are available to compare. Glycolate is widely accepted to be harmless, even at elevated values, but a fundamental proof is missing. So, consequences of this need further investigation.
Funding
- Government Support – Non-U.S.