Influence of allograft size to recipient body-weight ratio on the long-term outcome of renal transplantation

Background: The critical nephron mass needed to meet the metabolic demands of an individual depends on the body-weight, This study evaluated the effec t of the kidney transplant ultrasonographic size to recipient body-weight r atio (Tx/W) on the outcome of kidney transplantation. Methods: A consecutive series of 104 cadaveric renal transplants was studie d. Transplant cross-sectional area (TXSA) Tvas measured ultrasonographicall y in the first: week after transplantation as an index of renal size. A 'ne phron dose' index (Tx/W) was calculated by dividing TXSA by recipient weigh t and was used to define three groups of patients, with high (more than 0.4 5), medium (0.3-0.45) or low (less than 0.3) Tx/W ratios. Isotope glomerula r filtration rate (GFR) measurements were made at 1, 6 and 12 months after transplantation. Results: The serum creatinine level was significantly lower in the first 5 years after transplantation in patients with a high Tx/W ratio than in thos e with a medium or low ratio. GFR measurements were marginally higher in th e groups with a high. and medium Tx/W ratio compared with the low Tx/W grou p, A statistically significant association between Tx/W ratio and graft sur vival was not found. Conclusion: The renal transplant size to recipient weight ratio was an impo rtant determinant of long-term renal allograft function in this study. Extr eme mismatching between allograft and recipient size should be avoided wher e possible, but the findings presented require confirmation in larger studi es before clear recommendations can be made about; size matching and kidney allocation.