Nephrol Dial Transplant (1992) 7: 1254-1260 © 1992 European Dialysis and Transplant Association-European Renal Association
Nephrology Dialysis Transplantation
Inulin infusion technique in ADPKD Sir, In their study on the response of the GFR to amino acids of patients with autosomal dominant polycystic kidney disease and glomerular disease, Zeier and co-workers used the steady-state inulin infusion technique [1]. This technique was introduced by Berger et al. in 1948 [2]. Berger et al. reported a good agreement between bladder clearances (C = U x V/P) and clearances calculated by the constant intravenous infusion technique (C = I x V/P) in normal subjects, and fair agreement during acute changes in filtration rate and renal plasma flow. Unsuccessful attempts to use the infusion technique resulted from failure to attain equilibrium between IV and UV, especially in the presence of oedema, and they noted that this technique may be erronous in short experiments in subjects whose clearances are less than 60% of normal. In The Kidney: Structure and Function in Health and Disease, Homer W. Smith writes: 'The technique is sound in principle, but the investigator should satisfy himself of his competence to check bladder clearances by this method. Workers in the writer's laboratory have been rather disappointed in this respect and have not substituted the infusion technique for bladder clearances in any important study, even in those extending over periods of 24 hr. where it would be most useful. It seems probable that, as Landowne and Alving note, a prolonged period of time is required for a change in renal function to be reflected in significant changes in plasma concentration. This will be more important with PAH, which penetrates some tissues, than with inulin, which is distributed only in the extracellular fluid; but even with inulin there is relatively slow mixing in the extracellular fluid and opportunity for large errors'. [3]. In 1971 we described, among others, the relationship between the clearance of inulin according to C = U.V/P (y) and the clearance of inulin according to C = I.V/P (x) in 30 patients with various grades of renal impairment, and found j'=1.06.r-7.64 (r = 0.98, p
Nephrology Dialysis Transplantation
Inulin infusion technique in ADPKD Sir, In their study on the response of the GFR to amino acids of patients with autosomal dominant polycystic kidney disease and glomerular disease, Zeier and co-workers used the steady-state inulin infusion technique [1]. This technique was introduced by Berger et al. in 1948 [2]. Berger et al. reported a good agreement between bladder clearances (C = U x V/P) and clearances calculated by the constant intravenous infusion technique (C = I x V/P) in normal subjects, and fair agreement during acute changes in filtration rate and renal plasma flow. Unsuccessful attempts to use the infusion technique resulted from failure to attain equilibrium between IV and UV, especially in the presence of oedema, and they noted that this technique may be erronous in short experiments in subjects whose clearances are less than 60% of normal. In The Kidney: Structure and Function in Health and Disease, Homer W. Smith writes: 'The technique is sound in principle, but the investigator should satisfy himself of his competence to check bladder clearances by this method. Workers in the writer's laboratory have been rather disappointed in this respect and have not substituted the infusion technique for bladder clearances in any important study, even in those extending over periods of 24 hr. where it would be most useful. It seems probable that, as Landowne and Alving note, a prolonged period of time is required for a change in renal function to be reflected in significant changes in plasma concentration. This will be more important with PAH, which penetrates some tissues, than with inulin, which is distributed only in the extracellular fluid; but even with inulin there is relatively slow mixing in the extracellular fluid and opportunity for large errors'. [3]. In 1971 we described, among others, the relationship between the clearance of inulin according to C = U.V/P (y) and the clearance of inulin according to C = I.V/P (x) in 30 patients with various grades of renal impairment, and found j'=1.06.r-7.64 (r = 0.98, p
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