long - term follow - up of donors has been advocated not only for the individual donor 's benefit but also to establish analyzable databases to improve the selection of future donors . the long - term safety of a living donation has been reported in young , healthy , caucasian kidney donors . in japan , besides the racial difference , the proportion of medically complex donors , such as those of advanced age or with hypertension is greater . there is a need for data on long - term outcomes in such donors . to date , there are only a few single - center reports from japan about long - term outcomes of living donors . most donors are lost to follow - up . in this study , we evaluated the long - term consequences of kidney donation , including the follow - up rates in our center . between january 1990 and december 2013 , a total of 124 living donor kidney transplants were performed . the data including the date of transplantation , the date of the last follow - up , donor 's age , sex , their relationship to the recipient , kidney function , proteinuria , and the prevalence of hypertension were collected , reviewing the respective medical charts . donors were assessed on whether they were currently followed up or not . being followed up was defined as either having clinic visits within a year or future appointments . of those not being followed up , the status of those donors was assessed , and they were divided as a dropout , referred to other institutions , or died . we assessed whether there was a difference in the follow - up rates depending on the relationship of the donor to the recipient or the age of the donor . we also assessed the donor outcomes in terms of their kidney function , proteinuria , and the prevalence of hypertension . the new equation proposed by the japanese society of nephrology was used to calculate the estimated glomerular filtration rates ( egfrs ) , as follows : egfr = 194  ( creatinine ) 1.094  age 0.287 ( or  0.739 if female ) . the research ethics board of our institution approved this study , and the research was conducted in accordance with the ethical standards of the helsinki declaration . we used chi - square and fisher exact tests for categorical data and student 's t - test variance for continuous data . statistical analyses were conducted using spss version 16 ( spss inc . , chicago , il , usa ) . we used chi - square and fisher exact tests for categorical data and student 's t - test variance for continuous data . statistical analyses were conducted using spss version 16 ( spss inc . , chicago , il , usa ) . the mean age of the donors at the time of donation was 57.6 years ( standard deviation : 10.5 ) , and 74 ( 59.6% ) of them were women . the mean follow - up duration was 4.3 ( 3.6 ) years . when donors were categorized as parents , spouses , brothers or sisters , and others , in terms of their relationship to the recipients , most of the donors were either parents ( 57.2% ) or spouses ( 28.2% ) . of 124 donors , 52 donors ( 41.9% ) were not being followed up [ figure 1 ] . follow - up rates were 83.9% , 74.6% , and 59.2% at 1 year , 2 years , and 5 years postdonation , respectively [ figure 2 ] . of those not being followed - up , only 10 donors ( 19.2% ) were referred to other institutions and most of them ( 75.0% ) dropped out [ figure 3 ] . two donors had died , one of traffic accident and the other of colon cancer . follow - up rates between parent and spouse donors did not differ at 1 year ( 83.1% vs. 88.6% ; p = 0.5 ) and 5 years ( 57.1% vs. 71.4% ; p = 0.4 ) postdonation [ figure 4 ] . when donors were categorized according to age , 61 donors ( 49.2% ) were aged 60 years or older , and 63 donors ( 50.8% ) were younger than 60 years old [ table 1 ] . follow - up rates did not differ between donors aged 60 years or older and those younger than 60 at 1 year ( 79.4% vs. 88.5% ; p = 0.2 ) and 5 years ( 57.5% vs. 61.3% ; p = 0.6 ) postdonation [ figure 5 ] . of 72 donors being followed up , 75.0% ( n = 54 ) had egfr of < 60 ml / min/1.73 m and their mean egfr was 52.9  10.2 ml / min/1.73 m [ table 2 ] . similarly , 8.3% ( n = 6 ) had a significant proteinuria defined as the presence of urinary protein exceeding 0.3 g/24 h or 0.3 g / gcr and 41.7% ( n = 30 ) had hypertension requiring medication . baseline characteristics of the donors follow - up rates of donors follow - up rates of donors at 1 year , 2 year , and 5 years postdonation details of donors not being followed - up follow - up rates of parent and spouse donors at 1 year and 5 years postdonation follow - up rates of donors aged 60 years or older and those younger than 60 at 1 year and 5 years postdonation baseline characteristics of the donors being followed - up donor safety is the fundamental principle of living donor kidney transplantation , which is performed with the acceptable safety of kidney donors in mind . the long - term safety of donors postdonation has recently been documented in several reports . on the other hand , there definitely are donors who develop significant proteinuria or declined renal function corresponding to chronic kidney disease ( ckd ; stage 3 or higher ) , and end - stage renal disease ( esrd ) after donation . incidence of esrd in living kidney donors has been reported to be 0.7% with a median time of 20 years from donation to esrd . thus , not only the recipients but also the donors need to be followed up for a long time . likewise , there was no national registry for donor follow - up , making it difficult to report on the long - term outcomes of living donors . our center is one of the few centers in japan that have strongly encouraged donors to be followed up at their own institution to avoid being lost to follow - up . in this study , we evaluated the follow - up rates of living kidney donors in our center . the 5-year follow - up rate of 59.2% at our center was much better than that of a previous report from japan , which reported a 5-year follow - up rate of 21.3% . in this study , we confirmed that there is a wide difference in the actual follow - up rates between transplants centers . the higher follow - up rate at our center is probably because we strongly encourage annual clinic visits and laboratory checks for donors . it is a matter of concern that only one - fifth of those not being followed up were referred to other institutions . furthermore , once donors were referred to other institutions , data on blood pressure and kidney function were rarely received at the transplant center . in the united states , only 5% of the programs received data on 75% or more of their donors from primary care physicians . this suggests that there are limitations to the endeavors of transplant centers to follow - up all their donors and makes it reasonable to establish a national registry for donor follow - up . follow - up rates did not differ between parent and spouse donors , 1 year and 5 years postdonation , respectively [ table 1 ] . similarly , follow - up rates did not differ between donors aged 60 or older and those younger than 60 , 1 year and 5 years postdonation . we expected that spouse donors would have better follow - up rates as they usually live with their recipients who regularly attend transplant clinics after kidney transplants . we also expected that older donors would have better follow - up rates as most of them are retired with more free time and they typically have a stronger interest in their health than the younger generation . our results showed that equally strong education is needed in these subgroups to prevent them from getting lost to follow - up . most of the donors in japan are known to develop ckd stage 3 after donation . in our study , 75.0% of the donors had egfr of less than 60 ml / min/1.73 m and classified as ckd stage 3 . 8.3% had a significant proteinuria , and 41.7% had hypertension requiring medication , which were similar to previous reports . although kidney donors convey minimal risk of esrd in the absence of any other markers of kidney disease , some donors do develop risk factor of ckd and require close follow - up . there are a number of barriers to providing long - term donor follow - up . cost issues are also common . donors often consider themselves healthy and stop visits to the clinic by their own judgment . for these reasons , many physicians involved in the care of living kidney donors have encountered difficulties in providing long - term care . although living kidney donation is common , substantial variation exists between transplant programs with regard to how a potential donor is screened and which exclusion criteria are used . more widespread and long - term follow - up of living donors would provide important registry data . these data would ultimately improve the evaluation of potential living donors , especially those who are medically complex . all donors should be followed up continuously , at least once a year , but more often , especially if they are at risk of ckd progression . they should be carefully checked not only for the decline of renal function but also for the development of any new risks of ckd or cardiovascular disease , which subsequently need to be managed .
long - term follow - up of kidney donors is needed not only for the individual donor 's benefit but also to establish analyzable databases to improve the selection criteria for future donors . 
 we collected data including the date of transplantation , the date of the last follow - up , donor 's age , sex , their relationship to the recipient , renal function , proteinuria , and the prevalence of hypertension . 
 of 124 donors , 52 donors were not being followed up . 
 the mean duration of follow - up was 4.3  3.6 years . 
 follow - up rates were 83.9% , 74.6% , and 59.2% at 1 year , 2 years , and 5 years postdonation , respectively . 
 of those not being followed up , 75% dropped out . 
 follow - up rates did not differ between parent and spouse donors 5 years ( 57.1% vs. 71.4% ; p = 0.4 ) postdonation . similarly , follow - up rates at 5 years did not differ between donors aged 60 years or older and those younger than 60 ( 57.5% vs. 61.3% ; p = 0.6 ) 
 . of 72 donors being followed up , 75.0% had estimated glomerular filtration rate of < 60 ml / min/1.73 m2 , 8.3% had proteinuria , and 41.7% had hypertension requiring medication . 
 there is a limitation to the endeavor of each transplant center to follow - up all their donors . 
 long - term donor follow - up in japan requires a national registration system and mandates transplant center participation .