Kidney-Recipient Weight Incompatibility May Decrease Long-Term Graft Survival

Laurie Barclay, MD

September 18, 2010

May 20, 2010 — Incompatibility between kidney graft size and recipient weight independently predicts lower long-term graft survival, according to the results of a multicenter cohort study reported online in the May 20 issue of the Journal of the American Society of Nephrology.

"Long-term function of kidney allografts depends on multiple variables, one of which may be the compatibility in size between the graft and the recipient," write Magali Giral, MD, PhD, from Centre Hospitalo Universitaire de Nantes, France, and colleagues. "The effect of kidney graft size [Kw] and recipient weight (Rw) has also been studied; however, the direct impact of matching the Kw itself (which correlates with both glomerular volume and nephron number) to the Rw has been studied only in relatively small cohorts of <300 patients and only in living donors, where the graft does not incur the same accumulating injuries as those from deceased donors."

The investigators evaluated the long-term effects of the ratio of Kw to Rw in 1189 patients who received a kidney transplant between 1995 and 2006. Among patients with a low Kw:Rw ratio (<2.3 g/kg), the graft filtration rate increased by a mean of 5.74 mL/minute from the third to the sixth month after transplantation (P < .0001), remained stable from 6 months to 7 years, then decreased at a mean rate of 3.17 mL/minute per year (P < .0001).

"This information is potentially useful for thousands of transplantations and provides a new opportunity to improve long-term graft survival," senior author Jean Paul Soulillou, MD, from the Institut National de la Santé et de la Recherche Médicale in Nantes, said in a news release.

Risk for proteinuria, use of more antihypertensive drugs, and segmental or global glomerulosclerosis were also greater in patients with low Kw:Rw ratios, and these patients had a 55% increased risk for transplant failure by 2 years of follow-up.

"[I]ncompatibility between graft and recipient weight is an independent predictor of long-term graft survival, suggesting that avoiding kidney and recipient weight incompatibility may improve late clinical outcome after kidney transplantation," the study authors write.

In an accompanying editorial, Ron Shapiro, MD, from the University of Pittsburgh in Pennsylvania, notes that living donors made up less than 1% of the case material for the study; therefore, these findings may not be generalizable to living donor kidneys or to those from very young pediatric donors.

"These observations represent a new and elegant way of quantifying the potentially negative effect of nephron underdosing and make the additional point that this effect takes a longer time to appear after transplantation than we once thought," Dr. Shapiro writes. "[I]t will be important to replicate these provocative observations of Giral et al. in other large cohorts of patients with sufficiently long follow-up. In the meantime, the authors are to be congratulated for describing a novel measure that may have important implications for long-term outcomes in renal allograft recipients."

The study authors and Dr. Shapiro have disclosed no relevant financial relationships.

J Am Soc Nephrol. Published online May 20, 2010.

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