Size does matter for renal transplant outcomes

In an interesting study from France (Giral et al, JASN express May 20, 2010), effects of nephron underdosing on long term allograft function were studied. The novel marker used in the study was ratio of the weight of kidney before implantation (Kw) to the weight of recipient (Rw) i.e Kw/Rw. In a multicenter cohort of 1189 transplant recipients with mean follow up of 6.2 years, those with Kw/Rw < 2.3 g/kg had worse long term graft survival, more GFR decline, more proteinuria, more hypertension and more glomerulosclerosis than those with Kw/Rw > 2.3 g/kg. Low nephron mass (relative to recipient weight) with resultant chronic functional overload likely forms basis for the study findings. The main caveat of the study is absence of data on outcomes with transplantation of kidneys from pediatric donors. In an earlier study, outcomes of adults who undergo transplantation with pediatric kidneys were comparable to those from older donors (Zhang et al, cJASN, 2009). It would be interesting to see if current study findiings replicate in other studies.