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Primary hyperoxaluria (PH) type 1 and type 2 are autosomal recessive defects of oxalate metabolism resulting from glyoxylate accumulation which occurs by two distinct pathways. PH1 is associated to glycolic aciduria; PH2 to L-glyceric aciduria. Because hyperoxaluria leads to nephrolithiasis or nephrocalcinosis in both, they can be differentiated only through detection of the associated acidurias. However, glycolate and L-glycerate assays are not widely available and, in the setting of ESRF, diagnosis is hampered by a number of misleading events. At any stage of the disease diagnosis is crucial because there are differences between the two forms in clinical behaviour, long-term prognosis, and treatment. In this paper we outline diagnostic criteria for identification of PH2 in two patients, one with maintained renal function and one with ESRF on CPD, based on the use of a novel HPLC assay of L-glycerate in different body fluids. With the routine application of this procedure PH2 has been identified in two of 23 patients fulfilling criteria for diagnosis of PH. This suggests that the type 2 variant of PH may occur more frequently than so far suspected, and should be tested for even in the setting of ESRF. [ABSTRACT FROM PUBLISHER]

Systemic oxalosis is a constant feature in patients with primary hyperoxaluria type 1 (PH1) and chronic renal failure (CRF) and is not prevented by regular dialysis (RDT), because removal cannot keep up with retention and overproduction of oxalate. These patients are candidates to kidney and/or liver transplantation, which should be ideally planned prior to the development of oxalosis. However, methods to detect the presence and extent of oxalosis are invasive and poorly reproducible, and only indirect approaches are feasible. Because supersaturation of body fluids is an essential condition for oxalotic deposits to form, we have assessed serum calcium oxalate saturation (β) in 12 patients with PH1 and 26 with PH1-unrelated renal diseases and varying degrees of CRF. Nineteen healthy individuals were taken as controls. β was closely dependent on oxalate serum levels. Serum oxalate and β were increased in patients with CRF as compared to controls, and were inversely related to GFR, assessed as creatinine clearance. However, at any level of GFR, both were always greater in PH1 patients. From the slopes of the regression of β over CICr, saturation was predicted to be obtained at CICr ranging 24–34 and 8–11 ml/min/1.73 m in PH1 and non-PH1 patients respectively. Based on the dependence of β on oxalate, saturation was associated with serum oxalate between 44 and 46 µmol/l, irrespective of either the prevailing GFR or the underlying disease. These simple procedures represent a valuable non-invasive tool to define the risk of systemic oxalosis and may assist in timing of transplantation. [ABSTRACT FROM PUBLISHER]