Purpose: Chronic rejection accounts for the majority of late renal graft losses and there is good evidence that both immunologic and non-immunologic factors are important in late graft loss. The hyperfiltration hypothesis postulates that kidneys with reduced renal mass will progress toward failure due to hypertrophy of the remaining nephron to meet the excess metabolic demand, eventually leading to nephron exhaustion. The impact of metabolic demand and renal mass supply on the early graft function, especially hyperfiltration phenomenon, remains uncertain.
Methods: In this study, we analyzed age, gender, body weight, height, body surface area (BSA), lean body weight (LBW), and serum creatinine (SCr) of both donors and recipients. We weighed the donated kidney and measured the recipient’s SCr and LBW for six months postoperatively. Modified Cockcroft-Gault Equation standardized for BSA was used to calculate renal glomerular filtration rate (CrCl, mL/min/1.73 m2). The variables and the CrCl of the 3rd day and 6th month were analyzed with accordance to donor/recipient LBW ratio(D/R LBW) and graft weight/recipient LBW (GW/RLBW) by independent sample t-test and paired t-test using SPSS, and P<.05 was considered significant.
Results: The means of the 3rd day and 6th month CrCl were 76.90+/-24.35 and 73.41+/-10.80, respectively and there were no statistical differences (P=0.340). In D group (D/R LBW>1), the 3rd day and 6th month CrCl were 80.82+/-28.74 and 71.66+/-12.12, respectively. In R group (D/R LBW< or =1), the 3rd day and 6th month CrCl were 69.94+/-12.06 and 75.80+/-7.24, respectively. D group CrCl was decreased (P=0.093) and R group CrCl was increased slightly (P=0.169) during the study period, but there was no statistical significance. In H group (GW/RLBW>3), the 3rd day CrCl was 86.08+/-25.13, which was significantly decreased to 73.48+/-11.64 at the 6th month (P=0.023). In L group (GW/RLBW< or =3), the 3rd day and 6th month CrCl were 66.95+/-19.94 and 73.34+/-10.60 (P=0.158), respectively. the 3rd day CrCl of H group was higher than that of L group significantly (P=0.047), but 6th month CrCl showed no difference between the two groups (P=0.975).
Conclusion: The 3rd day CrCl represents early graft function well. GW/RLBW has a strong correlation with early graft function. In L group with low early graft function, CrCl was tended to be increased to meet the metabolic demand for following the 6 months. Conversely, in H group with high early graft function, CrCl was decreased to reduce the excess graft function. So the 6th month CrCl represents adapted graft function. In this study, therefore, we postulate that the hyperfiltration or hypofiltration develops according to metabolic demand and renal mass supply.
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