The aim of this study was to determine the appropriate body mass index (BMI) in Japanese kidney transplant (KTx) recipients. We analyzed the effects of pre- and post-transplant (Tx) obesity on graft and patient survival, perioperative complications, post-transplant diabetes mellitus (PTDM), and cardiovascular disease (CVD) in Japanese KTx recipients.
This retrospective study included 269 recipients who underwent KTx from 2008 through 2020 at Niigata University Hospital. Obesity was defined as a body mass index (BMI) ≥25 kg/m. We examined the association between pre- and post-Tx obesity and graft survival, patient survival, the incidence of PTDM and CVD, and perioperative surgical complications.
The graft survival rate was lower in the pre-Tx BMI ≥25 kg/m group, although there was no significant difference in patient survival. There was no difference in graft and patient survival between the post-Tx BMI ≥25 kg/m group and the <25 kg/m group. A pre-Tx BMI ≥25 kg/m was an independent risk factor for biopsy-proven allograft rejection. New-onset DM after transplantation was significantly more common in the BMI ≥25 kg/m group than in the BMI <25 kg/m group (36% vs 13%; P = .002). The incidence of CVD was significantly higher in the post-Tx BMI ≥30 kg/m group than in the BMI <30 kg/m group (50% vs 11%; P = .023). There were no differences in surgical operating time, intraoperative blood loss, or perioperative complications between the obese and non-obese groups.
Pre-Tx BMI ≥25 kg/m may be a risk factor for allograft rejection and graft loss. Post-Tx BMI should be <25 kg/m to reduce the risk for PTDM.

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