Calcium-oxalate (CaOx) crystal deposition is uncomon in children with renal insufficiency (CRI), but frequent in children with PH I who have normal renal function. We hypothesized that there would be a difference in plasma CaOx saturation (βcaox) and its determining factors to explain this. Therefore, we measured plasma oxalate (Pox), citrate (Pcit) and sulfate(Psulf) and calculated βcaox in 20 PH I patients with normal renal function, with B6 and citrate therapy. They were compared to 50 healthy children (NL) and 56 non-PH-patients with CRI (Screa: 0.9 - 5.9 mg/dL). Anions were analyzed via ionchromatography (DX 500, Dionex Corp.), as we have previously described. βcaox was calculated using a PC-based equilibrium program. Results in μmol/L, mean(±SE): Table All parameters were significantly elevated in PH I and CRI. Pox, Pcit and βcaox were higher in PH I than in CRI(p<0.01). βcaox and Pox were correlated in all groups (r=0.63-0.98, p<0.0001). 7 (CRI) and 5 (PH I) patients had βcaox > 1.0(supersaturated). Conclusions: In PH I Pox and βcaox are elevated even with normal renal function, possibly leading to CaOx crystal deposition. Although Pcit increased under citrate therapy compared to NL, it did not adequately lower βcaox. Therefore, more effective therapy to decrease βcaox is crucial to reduce the risk of systemic oxalosis. In CRI unknown, but presumably protective substances may help prevent the risk of CaOx deposition, despite increased Pox and βcaox levels often above supersaturation.

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