Histological assessment of pre-implantation allograft biopsies: does it matters?

Correspondence to: Mario Abbud Filho. Uro Institute. Rua Voluntarios de São Paulo, no 3826, São José do Rio Preto, SP, Brazil. CEP: 15015-200. E-mail: [email protected] We often face the dilemma of accepting or rejecting extended criteria or “high risk” kidneys and having to make a quick decision, usually in the middle of the night and without much time to think. Histological assessment by biopsy prior to implantation, also called zero-hour biopsy, may be useful to report on the status of the organ. However, the question that requires urgent answering is: can these biopsies predict the short and long term outcomes of these grafts and provide prognostic information, in addition to the chronic lesions associated with the donor kidney? The first recommendation for pre-implant biopsy was made in 1995, by Gaber et al., and since then several studies have sought to establish the predictive value of these biopsies, yielding controversial results.1 For instance, in Europe they rarely do pre-implantation biopsies, and extended criteria donor kidneys (ECD) are successfully transplanted, according to the program called Senior Kidney Transplant Program, while in the U.S. the discarding rate of these kidneys is about 40%.2-4 In this JBN issue, Pegas et al. tried to answer this question by retrospectively analyzing 110 pre-implantation biopsies (harvested in wedge shapes) from living donors (LD, n = 27), “standard” (SCD, n = 47) and expanded criteria (ECD, n = 36) kidneys. The vast majority of recipients was treated with calcineurin inhibitors (74%), mycophenolic acid (90%) and 30% received induction therapy with monoclonal anti-interleukin 2 receptor antibodies. The MDRD formula was used to calculate the glomerular filtration rate (GFR), which was correlated with the findings from the donor biopsy and classified according to the Remuzzi criteria.5 The outcomes were analyzed after one year of transplantation and, as expected, the authors found that LD recipients had better GFR rates than recipients from deceased donors. Also, GFR rates from SCD recipients were better than their ECD counterparts, regardless of histological findings. Still, kidneys with mild histological changes had GFR rates better than those with moderate/intense lesions. The one-year survival of 110 recipients studied was not different when stratified according to histological scores (mild, moderate, severe), although the survival of the population whose kidneys showed marked lesions was numerically lower. Using multivariate analysis applied to the entire study population, the authors showed that the lesions from glomerulosclerosis and atherosclerosis were significantly associated with lower rates of GFR after 1 year. However, the same analysis carried out for the population of deceased donors only showed association between GFR and glomerulosclerosis. Unfortunately, Pegas et al. did not report, even if only for discussion purposes, the GFR results from ECD and SCD correlated with the histological scores used to evaluate the different kidney compartments. Moreover, and as acknowledged by the authors themselves, their study had limitations that prevented definitive conclusions: a small sample, a group of heterogeneous biopsies from