[The critical value of residual kidney function in patients with chronic kidney failure from the viewpoint of the concentration of urea and potassium in the plasma].

Residual kidney function was examined in 10 patients with chronic renal insufficiency under balance conditions and in 30 outpatients on the basis of urea clearance (Curea) and potassium clearance (CK). Protein intake was 35-40 g/day (0.5 g/kg/day) and potassium intake was 30-40 mmol/day. Under these conditions the critical values of residual kidney function were as follows: 1) plasma urea concentration (Purea) did not exceed 30 mmol/l if Curea did not drop below 3.8 ml/min; 2) plasma potassium concentration (PK) did not exceed 5 mmol/l if CK did not decrease below 4.1 ml/min. Clinical examination of Curea and CK provides additional information to the examination of creatinine clearance (Ccr) or its plasma concentration (Pcr). Our results suggest that the critical value of residual kidney function cannot be defined only on the basis of examination of Ccr or Pcr. Examination of Curea and CK can help in the interpretation of very high Purea and hyperkalemia in patients with chronic renal insufficiency.