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Volume: 15 Issue: 1 February 2017 - Supplement - 1

FULL TEXT

Obesity and Loss of Kidney Function: Two Complications to Face for Older Living Kidney Donors

Objectives: Although living kidney donors have a minimal lifetime risk of developing end-stage renal disease, long-term complications and physiologic and psychologic sequelae resulting from donation remain unclear because of lack of optimum follow-up after transplant. Here, we evaluated renal function, com­plications, and physical and mental performance of living kidney donors.

Materials and Methods: We evaluated 147 patients who donated living kidneys between 1981 and 2012 at Baskent University Hospital. We collected data on donor age, sex, body mass index, smoking status, hypertension before and after nephrectomy, pro­teinuria, estimated glomerular filtration rate according to the Modification of Diet in Renal Disease formula, and duration after donation. All donors answered the Medical Outcomes Study short-form general health survey; results were evaluated according to answers to 11 questions totaling 22 points.

Results: Body mass index of donors showed that 31 (21.1%) were in normal range, 66 (44.9%) had mild obesity (body mass index of 26-30 kg/m2), and 30 (34%) had moderate to high obesity (body mass index > 30 kg/m2). Results from the general health survey showed that 117 donors (80%) had no loss, 13 (9%) had mild loss, 12 (8%) had moderate loss, and 5 (3%) had high loss of ability. When we compared estimated glomerular filtration rates according to donor age, donors who were 18 to 34 years had a mean estimated glomerular filtration rate of 113.5 ± 40, donors 35 to 49 years had a mean rate of 95.01 ± 23.4, donors 50 to 64 years had a mean rate of 87.43 ± 25.4, and donors older than 65 years had a mean rate of 63.76 ± 11.35 mL/min/1.73 m2, revealing a statistically significant loss of kidney function with aging (P = .001).

Conclusions: Careful evaluation of kidney donors before and after donation is essential for the most common risk factors, such as obesity, and for loss of kidney function, especially in older donors.


Key words : Ability, Kidney function, Long-term, Survival, Transplantation

Introduction

Kidney transplant is the treatment of choice for patients with end-stage renal disease because it offers improved survival and better quality of life.1 Unfortunately, the number of deceased donors is inadequate to supply the increasing number of patients with end-stage renal disease needing kidney transplants; therefore, living kidney donations now account for more than 80% of all donations.2 Most epidemiologic studies have suggested that living kidney donors have a minimal lifetime risk of developing end-stage renal disease; however, long-term complications for the donors and physiologic and psychologic sequelae resulting from donation remain unclear because of the lack of optimum follow-up of donors after kidney transplant.3-7

In our study, we analyzed the renal function, presence of new-onset proteinuria, and obesity and hypertension status of our living kidney donor population and determined the physical and mental performance of these donors using the Medical Outcomes Study (MOS) short-form general health survey.

Materials and Methods

We evaluated 147 patients who donated living kidneys between 1981 and 2012 at Baskent University Hospital. Our cohort had a mean age of 44 years at the time of donation. We collected data on donor age, sex, body mass index, smoking status, hypertension before and after nephrectomy, presence of proteinuria, estimated glomerular filtration rate (eGFR) according to Modification of Diet in Renal Disease formula, and duration after donation. Hypertension was defined as systolic blood pressure > 140 mm Hg, diastolic blood pressure > 90 mm Hg, or the use of antihypertensive medications. Donor proteinuria was confirmed by dipstick test and proteinuria-to-creatinine ratio. All donors answered the MOS short-form general health survey; the results were evaluated according to answers to 11 questions totaling 22 points. Patients were divided into 4 groups according to the results: living kidney donors with ≥ 13 points had heavy loss of ability, those with 8 to 12 points had moderate to high loss of ability, those with 5 to 7 points had mild ability loss, and those with ≤ 4 points had no ability loss.

Statistical analyses were performed with the Statistical Package for the Social Sciences software (version 16.0, SPSS Inc, Chicago, IL, USA). All numerical variables are expressed as means ± standard deviation. Normality of data was analyzed by using the Kolmogorov-Smirnov test. All numerical variables with normal distribution were expressed as means ± standard deviation, whereas variables with a skew distribution were expressed as median (interquartile range). Categorical variables are given as percentages and were compared with the chi-squared test. Normally distributed numeric variables were compared with independent samples of t test, and skew-distributed numeric variables were compared with the Mann-Whitney U test. A P value of .05 was accepted as statistically significant.

Results

The mean age of our donor group was 50.05 ± 11.73 years at the time transplant. Approximately 6 years after donation, type 2 diabetes mellitus was diagnosed in 7 donors (5%), hypertension was diagnosed in 20 donors (14%), and coronary artery disease was diagnosed in 5 donors (3%), with no systemic disease diagnosed in 115 donors (78%). Body mass index results showed that 31 donors (21.1%) were in the normal range, 66 (44.9%) had mild obesity (body mass index = 26-30 kg/m2), and 30 (34%) had moderate to high obesity (body mass index > 30 kg/m2). In our study group, 53 donors (36%) were parents, 38 donors (26%) were brothers or sisters, 35 donors (24%) were husbands or wives, 11 donors (7%) were sons or daughters, and 10 donors (7%) were third-degree relatives.

According to the MOS short-form general health survey, 117 donors (80%) had no loss of ability, 13 (9%) had mild loss of ability, 12 (8%) had moderate loss of ability, and 5 (3%) had high loss of ability after transplant. When we compared eGFRs according to donor age groups, donors who were 18 to 34 years old had a mean eGFR of 113.5 ± 40 mL/min/1.73 m2, donors who were 35 to 49 years old had a mean eGFR of 95.01 ± 23.4 mL/min/1.73 m2, donors who were 50 to 64 years old had a mean eGFR of 87.43 ± 25.4 mL/min/1.73 m2, and donors who were older than 65 years had a mean eGFR of 63.76 ± 11.35 mL/min/1.73 m2. These results showed a statistically significant loss of kidney function with aging (P = .001).

In our center, the lower limit of total GFR to be a kidney donor is 100 mL/min/1.73 m2. At the time of the study, we found that 72 donors (49%) had a mean eGFR above 90 mL/min/1.73 m2, 62 donors (42%) had a mean eGFR of 60 to 89 mL/min/1.73 m2, and 12 donors (8%) had a mean eGFR of 30 to 59 mL/min/1.73 m2. There were no kidney donors with a mean eGFR lower than 30 mL/min/1.73 m2. When we compared patients according to the time after donation, 43 donors (46.7%) at 1 to 5 years after donation had mean eGFRs of > 90 mL/min/1.73 m2, with 39 donors (42.4%) at 60 to 89 mL/min/1.73 m2 and 10 donors (10.9%) at 30 to 59 mL/min/1.73 m2. At > 5 years after donation, 29 donors (52.7%) had a mean eGFR of > 90 mL/min/1.73 m2, 23 donors (41.8%) had a mean eGFR of 60 to 89 mL/min/1.73 m2,and 3 donors (5.5%) had a mean eGFR of 30 to 59 mL/min/1.73 m2. Duration after kidney donation was not statistically associated with eGFR results in our patient group.

Neither donor age nor duration after donation was found to be associated with obesity and hypertension, and obesity was also not found to be associated with hypertension in our study group.

Discussion

Hypertension, diabetes, obesity, and loss of kidney function are the major complications for donors after kidney donation that should not be underestimated. Survival of kidney donors after donation remains controversial according to results of various studies. Some studies have reported that kidney donors had a better overall health status compared with age-matched controls, whereas others have reported an association between kidney donation and chronic kidney disease, end-stage renal disease, proteinuria, and hypertension, which may lead to morbidity and mortality.3-10 In our study, we showed that older donors had a statistically significant loss of kidney function compared with younger donors, but none of the donors in our group had an eGFR below 30 mL/min/1.73 m2. We suggest that a careful selection of donors with eGFRs of at least 100 mL/min/1.73 m2 before donation was the main reason for better survival of kidney function in our donors.

We used the MOS short-form general health survey to evaluate quality of life in our donor group after donation. There were no correlations between life quality and donor age, duration after donation, obesity, and hypertension in our patient group. This finding is similar to the satisfying effects of kidney donation discussed in some recent studies.11-13

In our study, we revealed a high incidence of obesity in our donor group. In a recent epidemiologic study in Turkey, obesity prevalence was reported to be 44% in women and 27% in men, which may reflect that obesity is an endemic problem in Turkey involving the donor group of our study.14 Despite obese donors being prone to developing new-onset hypertension, diabetes, and coronary artery disease, our patient population had no significant increase in these potential diseases.15-17 The mean follow-up of 6 years after donation may be a limiting factor for our patient group to diagnose new-onset diseases. We also do not accept marginal donor criteria in kidney transplants, which may explain the lower rates of new-onset hypertension, obesity, and loss of kidney function in donors.

Conclusions

In conclusion, donor selection criteria may be enlarged in our center after a longer and closer follow-up of kidney donors is applied. It is essential to carefully evaluate kidney donors both before and after donation for the most common risk factors, including hypertension, obesity, and loss of kidney function.


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Volume : 15
Issue : 1
Pages : 136 - 138
DOI : 10.6002/ect.mesot2016.P22


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From the 1Department of Internal Medicine, Baskent University Faculty of Medicine, and the 2Department of Nephrology, Baskent University Faculty of Medicine, Ankara, Turkey
Acknowledgements: The authors declare that they have no sources of funding for this study, and they have no conflicts of interest to declare.
Corresponding author: Burak Sayin, Baskent University Ankara Hospital, Fevzi Cakmak Caddesi, 5. Sokak, No: 48, 06640 Bahcelievler/Cankaya, Ankara, Turkey
Phone: +90 312 212 2912 ext. 5226
E-mail: buraksayin@hotmail.com