Residual kidney function and plasma urea concentration in patients with chronic renal failure

The relationships between the plasma levels of urea (Purea), renal clearance of urea (Curea) and creatinine (Ccr) at an intake of 0.5 g protein/kg body weight/day were followed in 10 patients with chronic renal failure (CRF) under balance conditions. Under these conditions, Purea attained a value of 30 mmol/l when Curea had decreased below 3.8 ml/min. By contrast, no correlation could be demonstrated between Purea and Ccr under these conditions.