ESPN 53rd Annual Meeting

ESPN 2021


 
Oxalate in urine and plasma related to kidney function, dialysis or transplantation in patients with primary hyperoxaluria type 1
CRISTINA MARTIN-HIGUERAS 1 JULIA PICK 2 BERND HOPPE 1

1- GERMAN HYPEROXALURIA CENTER
2- UNIVERSITY HOSPITAL BONN
 
Introduction:

Three different enzyme defects in primary hyperoxaluria (PH) lead to endogenous oxalate overproduction and extremely elevated urinary oxalate excretion (UOx), which induces recurrent urolithiasis, nephrocalcinosis and chronic kidney disease, the latter especially in PH1. Uox and plasma oxalate (Pox) are used as biochemical markers for diagnosis, treatment decisions and outcome parameters. We were interested in their long term follow up related to kidney function, hemodialysis (HD) or transplantation (Tx).

 

Material and methods:

We retrospectively analyzed biochemical data taken in genetically confirmed PH1 patients over the last 15 years. Both urine and plasma were analyzed for oxalate, glycolate (UGlyc/PGlyc) and creatinine (Crea). Data was examined by means of correlation/regression analysis within groups of different renal function (normal, CKD 1-5; n=56 patients), HD (n=26), post Tx (n=32), and over time.

 

Results:

Pox remained equivalent between stages of kidney function (median Pox 17 µmol/l). Until CKD 3-4 only 17% Pox values and 33% in CKD 5 were > 30. Highest Pox was found in HD (91) and HD post liver Tx (46 µmol/l) in sequential procedure. PGlyc was elevated in all groups of kidney function and significantly higher in HD (211 µmol/l). Correlations were found for Pox with PGlyc in CKD 3-4 (r=0.73; p<0.001), for Pox with SCrea (r=0.78; p<0.001) and negatively with eGFR in CKD 5 (r=-0.51; p<0.001) and for Uox with eGFR in normal kidney function (r=-0.24; p=0.04). Uox correlated to Pox in CKD 3-4 (r=0.77; p=0.004). Pox and Uox slowly declined over time in combined and sequential, but also in kidney Tx, which was only performed in adult B6-sensitive patients. PGlyc remained elevated post Tx.

Conclusions:

We did not find consistent correlation of either Pox or Uox to SCrea or eGFR. Pox was surprisingly low until HD. Long term follow up post Tx shows a slow decline in Pox and Uox in all transplant procedures.