Introduction: The compatibility between kidney graft size and recipient physique is a crucial factor in determining graft outcomes in kidney transplantation. However, donors and recipients with poorly matched physiques and ages are sometimes forced to undergo transplantation. This study examined the relationship between kidney volume and the physique of the recipient in living-donor kidney transplantation and considered the clinical course of recipients.
Materials and Methods: Between January 2018 and December 2022, 151 pairs of living-donor kidney transplants were performed. One patient was lost to follow-up due to acute myocardial infarction and died one month after transplantation. One patient underwent transplant nephrectomy immediately after transplantation because of irreversible hyperacute antibody-mediated rejection. One patient had an unexplained primary nonfunction. Six cases of graft rejection, three cases of BK virus infection, and one case of urinary tract infection resulted in irreversible damage to graft function. After excluding these 13 patients, 138 patients were included in the study. Donor kidney volume was estimated from computed tomography (CT) scans. The ratio of transplant kidney volume as determined on CT (CTV; mL) to recipient body mass index (BMI) (CTV / BMI) was determined before transplantation, and patients were grouped into low (L group; CTV / BMI <4.8; n = 45), medium (M group; CTV / BMI 4.8 to 6.0; n = 44) and high groups (H group; CTV / BMI > 6.0; n = 49). 
Results: CTV / BMI ratio, donor age, donor sex, and recipient age were significant predictors of eGFR at 12 months after transplantation (p<0.01, p < 0.01, p=0.003, and p=0.008, respectively). The CTV / recipient body weight ratio (CTV / Rw ratio), donor age, recipient sex, and donor sex were significant predictors of serum creatinine level at 12 months after transplantation (p<0.01, p=0.002, p=0.004, and p=0.011, respectively). Serum creatinine level at 12 months after transplantation correlated with the CTV / Rw ratio (R2 = 0.33; p< 0.001, y = 0.1248x2 - 0.892x + 2.5645). Serum creatinine levels at 12 months after transplantation in the L, M, and H groups were 1.48 ± 0.41, 1.35 ± 0.32, and 1.09 ± 0.26 mg/dL, respectively, with statistically significant differences (p<0.001).
Conclusion: A CTV/BMI ratio less than 4.8 is associated with significantly lower graft function. Matching the physique of the recipient to that of the donor is important in determining the outcome of kidney transplantation.