Background: So-called marginal kidneys are used increasingly in renal transplantation, but features of marginal kidneys are disputed.
Methods: To help define marginal, a morphometric measure, the index of chronic damage, was applied retrospectively to 500 implantation biopsy specimens of cadaveric grafts, and death-censored graft survival was calculated, up to 14 years after transplantation.
Results: An index of 0% (n=242) was associated with better survival than 1%, with little difference between 1% and 39% (n=249). An index of 40% or more (n=9) was associated with the worst survival (chi=14.2, 2 df, P <0.001). After controlling for donor age, the only values of the index related to survival were 40% and above (hazard ratio, 2.96; P =0.01). Donor age group 10 to 39 years old (n=238) had better survival than 1 to 9 years old (n=26) and 40 to 73 years old (n=236) (hazard ratios, 2.83 and 2.06, respectively; P <0.001). An early episode of acute rejection affected survival even at 6 years and later after transplantation (hazard ratio, 1.94; P <0.04).
Conclusions: Marginal kidneys are identified using the index of chronic damage, but they are so rare that measurement is not necessary on every graft. After routine graft allocation and in the absence of acute rejection, a kidney from virtually any donor in an age group has the same potential as a graft from nearly all others in that group.