M A S Ferreira1, A J Howie2, D Adu3 and G W Lipkin3
1Instituto de Urologia e Nefrologia, Rua Voluntários de São Paulo no 3826, Bairro Redentora, São José do Rio Preto - São Paulo, CEP 15015-200, Brazil, 2Department of Pathology, University of Birmingham, Birmingham, United Kingdom, and 3Department of Nephrology, University Hospital Birmingham NHS Trust, Birmingham, United Kingdom
Background. As the number of people on the waiting list for renal transplantation has risen, there has been increasing use of cadaveric donor kidneys considered marginal. There has been little work on features of the kidney that allow definition of “marginal”. A measure of the amount of irreversible damage in renal biopsy specimens, called the index of chronic damage, had been shown to indicate renal survival in series of non-transplant renal biopsies. The hypothesis of this study was that the index of chronic damage in implantation biopsies would predict long-term graft survival.
Methods. The index was measured retrospectively on implantation biopsies from 350 consecutive cadaveric grafts from 1988 to 1992 and on 150 selected biopsies out of the next 750 consecutive cadaveric grafts from 1992 to 2002, fifty selected because they had the most chronic damage, at least 10%, and the two grafts nearest in time to each of those fifty taken as controls. Donors were aged from one year to 73 years inclusive. Survival was studied by the Kaplan-Meier method with graft failure as the end point. Patients with a functioning graft were censored at the time of last follow-up and patients who died with a functioning graft were censored at death.
Results. The index ranged from 0% to 88%. Most biopsies, 432 out of 500, had under 10% damage, and only nine had 40% or more damage. There was a correlation between the age of the donor and the index (r = 0.60, P < 0.001, Spearman). When age was disregarded, an index of 1% was associated with significantly worse survival than an index of 0% and there was little difference in survival for indexes between 1% and 39% inclusive, but an index of 40% or more was associated with significantly worse survival than the rest (c2 = 14.2, 2 degrees of freedom, P < 0.001, log rank test). When age was taken into account the only value of the index that had a significant relation to graft survival was 40% or more. Compared with values of the index under 40%, the hazard ratio was 2.48 (95% confidence intervals (CI) 1.14 and 5.38, P = 0.02, Cox). Donor age could be put into three groups, 0-9 years (n = 26), 10-39 years (n = 235) and 40 years and above (n = 230), with little difference in survival between ages within the two largest groups but significantly better survival for the group aged 10-39 years compared with the other two. The hazard ratios for the group aged 10-39 years were 0.35 (CI 0.20, 0.62) compared with those aged 0-9 years (P < 0.001, Cox) and 0.51 (CI 0.37, 0.72) compared with those aged 40 years and above (P < 0.001, Cox). There was no significant difference in survival within these age groups between different values of the index when an index of 40% or more was excluded.
Conclusions. These findings show that the only amount of chronic damage in the implantation biopsy that had a relation to survival independently of donor age was 40% or more but that this was seen in hardly any grafts (nine out of 1100 in the whole series). Hardly ever can study of the amount of chronic damage in an implantation biopsy give a better indication of likely long-term graft survival than knowledge of the donor age.
Person to contact regarding acceptance of abstract:
Dra M A S Ferreira
Instituto de Urologia e Nefrologia,
Rua Voluntários de São Paulo no 3826,
São José do Rio Preto - São Paulo,
e mail: firstname.lastname@example.org