Long-term follow-up of the tubular secretion of creatinine in renal graft recipients

The differences in glomerular filtration rate (GFR) based on creatinine cle arance (C-cr) or obtained by the more exact methods are caused mainly by tu bular creatinine secretion. In this study, we monitored creatinine clearanc e (C-cr), GFR on the basis of polyfructosan renal clearance (C-PF) and para meters characterizing tubular creatinine secretion (C-cr/C-PF, C-cr - C-PF, T-cr/C-PF x 100) in 12 individuals with renal grafts (Group A), 12 kidney graft donors for related transplantation (Group B), and in 27 individuals u ndergoing nephrectomy for a pathological process in one kidney (Group C). I n the monitored groups, C-PF and Co values were within the limits consisten t with the normal function of a single kidney in a healthy individual. The values characterizing tubular creatinine secretion in Group A did not diffe r significantly from those obtained in Groups B and C. However, the paramet ers showed a wide range in all groups. In seven individuals with a renal gr aft, all the above functional parameters were monitored at three-month inte rvals for a period of 24 months. Significant differences in the time course s of Ccr and C-PF due to marked intra-individual fluctuations were found in tubular creatinine secretion. The findings suggest that the rate of tubula r creatinine secretion in the renal graft does not differ significantly fro m that in individuals with a single native (normally functioning) kidney. H owever, there are large inter-individual differences. The large intra-indiv idual fluctuations in tubular creatinine secretion in the kidney graft resu lt in significant differences in the time courses of C-cr and C-PF and a po ssibility of erroneous evaluation of graft function if based exclusively on C-cr.