Impact of Graft Mass on the Clinical Outcome of Kidney Transplants

Abstract

The effect of nephronic mass reduction of kidney transplants has not been analyzed specifically in a large cohort. Transplant injuries in cadaver kidney graft may have led to an underestimation of the magnitude of this factor. The aim of this study was to analyze the consequences of kidney mass reduction on transplantation outcome. The weights of 1142 kidney grafts were collected prospectively immediately before grafting. Donors and recipients <15 yr of age, simultaneous kidney/pancreas grafts, and technical failures before day 7 were excluded from the analysis. The analysis was performed on Cockroft-calculated creatinine clearance and proteinuria in 964 patients for whom all of the necessary information was available. This study reports that the smallest kidneys transplanted into the largest recipients (donor kidney weight/recipient body weight [DKW/RBW] <2 g/kg, n ‫؍‬ 88) increased their clearance by 2.38 ml/min every month for 6 mo (P < 0.0001) and by 0.27 ml/min thereafter (P < 0.0001). Conversely, creatinine clearance did not change for the largest kidneys transplanted into the smallest recipients (DKW/RBW ratios >4 g/kg). Next, using a Cox model analysis, it was shown that the risk of having a proteinuria >0.5 g/kg was significantly increased for the low DKW/RBW ratios <2 g/kg with 50% of patients having a proteinuria, compared with DKW/RBW ratios >4 g/kg (P < 0.001). In cadaver transplant recipients, graft mass has a rapid impact on graft filtration rate and proteinuria. Avoiding major kidney/recipient inadequacy should have a significant influence on long-term transplant function.

Kidney and Recipient Weight Incompatibility Reduces Long-Term Graft Survival

“…In this report, we reappraised our historical cohort 24 with a much longer survey period. We first tested whether a KwRw ratio incompatibility is an independent risk factor for subsequent hyperfiltration.…”

“…We previously reported on the results of a first study 24 focusing on the impact of graft weight on clinical outcome; however, within the relatively short survey period of the latter study (mean 32 months; range 8 days to 94 months), no impact on short-term graft survival was observed. Because renal failure has been described a decade after nephron reduction, 3,10,25 we reappraised our historical cohort to which an additional 47 patients were included (whole population n ϭ 1189) at a mean of 6.2 years from transplantation (range 8 days to 13 years).…”

The Clinical Importance of Nephron Mass

“…146 Similarly, among recipients of cadaveric kidneys, proteinuria was significantly higher and developed earlier in those with DKW/RBW Ͻ2 g/kg as compared with those with higher ratios, although 5-year graft survival was not different. 147 An ultrasound-based calculation of nephron dose index (Tx/W) incorporating cadaveric transplant kidney cross-sectional area (Tx) and recipient body weight (W) highlighted significantly better allograft function at 5 years in those with higher compared with lower Tx/W. 148 These data suggest small kidneys transplanted into large recipients may not have an adequate capacity to meet the metabolic needs of the recipient without imposing glomerular hyperfiltration, which may eventually contribute to nephron loss and allograft failure.…”

Determinants and Functional Significance of Renal Parenchymal Volume in Adults

“…For instance, a reduction can occur in chronic kidney disease and is a frequently used parameter for decisions about biopsy, whereas renal enlargement can occur in a number of disorders. Renal enlargement in diabetics is a risk factor for nephropathy (1,2), and the size of donor kidneys influences the outcome after transplantation (3)(4)(5). A reduced quantity of nephrons at birth may contribute to the development of hypertension (6,7) and may be detectable as differences in renal parenchymal volume because kidney weight correlates closely with nephron number (8) in healthy humans.…”