1. In order to find out whether hyperoxaluria can be demonstrated in patients on chronic (twice a week) haemodialysis, a group of 13 patients was investigated. These included one patient with proven primary hyperoxaluria, one suspected of having this disease and 11 patients in whom no information was available as to their oxalate metabolism.
2. Oxalate concentrations in haemodialysate fractions and blood samples, taken before and after dialysis, were determined.
3. The patient with primary hyperoxaluria had a plasma oxalate concentration before dialysis above 100 μmol/l and after dialysis above 25 μmol/l, while the oxalate concentration in haemodialysate at the start of dialysis was above 25 μmol/l and at the end above 10 μmol/l. The patient suspected of hyperoxaluria had similar values. Of the remaining 11 patients, one was shown to exhibit a transient hyperoxaluria, but the others showed a normal oxalate metabolism.
4. A plasma oxalate/creatinine concentration ratio exceeding 0.1, and the calculated total quantity of oxalate removed by dialysis exceeding 2 mmol, also enabled a diagnosis of hyperoxaluria to be made.
5. Hyperoxaluria can still be demonstrated in patients, who because of renal failure are subjected to haemodialysis. Measurements of oxalate in haemodialysate and plasma are valuable in cases where kidney transplantations are considered, especially when the particular patient exhibits hyperoxaluria.