Obesity in Living Kidney Donors: Clinical Characteristics and Outcomes in the Era of Laparoscopic Donor Nephrectomy

Abstract

Acceptance of obese individuals as living kidney donors is controversial related to possible increased risk for surgical complications and concern that obesity may contribute to long-term renal disease. We retrospectively examined 553 consecutive hand-assisted laparoscopic living kidney donations between October 1, 1999 and April 1, 2003. We stratified donors into quartiles by baseline body mass index (BMI) assessing perioperative complications and 6–12 months post-donation metabolic and renal function. Compared to BMI <25 kg/m², high BMI donors (≥35 kg/m²) had slightly longer operative times (mean increase 19 min), more overall perioperative complications (mostly minor wound complications), yet the same low rate of major surgical complications (conversion to open and re-operation) and similar length-of-stay (2.3 vs. 2.4 days). At 6–12 months after donation (mean 11 months), renal function and microalbuminuria did not differ with BMI. These results suggest that laparoscopic donor nephrectomy is generally safe in selected obese donors and does not result in a high rate of major perioperative complications. Obese donors have higher baseline cardiovascular risk and warrant risk reduction for long-term health. While early results are encouraging, we advocate careful study of obese donors and do not support their widespread use until longer follow-up is available.

Introduction

Over the past 30 years, the short- and long-term outcomes for living kidney donors have been excellent, although donation has generally been restricted to a selected donor group with near optimal health (1). Superior outcomes for recipients of living donor allografts combined with increasing deceased donor waiting times and a rise in prevalence of obesity have forced re-examination of donor selection criteria to consider obese individuals (body mass index (BMI) ≥ 30 kg/m²) who are otherwise in good health. Open surgical nephrectomy in obese subjects is associated with higher rates of post-operative complications, primarily wound related (2). The introduction of laparoscopic techniques facilitates use of obese donors and initial reports of laparoscopic nephrectomy describe comparable operative success to non-obese patients (3,4). Some centers report longer operative times and higher conversion rates for obese donors, though most complications are minor (5). Little is known about the baseline clinical characteristics and subsequent outcomes for obese donors beyond the perioperative period.

Based upon our living donor experience in the era of laparoscopic nephrectomy, we sought to examine cardiovascular risk factors, renal function and surgical outcomes of renal donation and their relation to obesity, using BMI as a standardized marker for the extent of obesity. We report results of a retrospective analysis of 553 consecutive living renal donors who underwent laparoscopic donor nephrectomy between 1999 and 2003 analyzed by quartiles according to BMI.

Materials and Methods

The study involved a retrospective review of the medical records of living renal donors who underwent laparoscopic donor nephrectomy at Mayo Clinic Rochester during the period from October 1, 1999 through April 1, 2003. The institutional review board of the Mayo Clinic approved the data collection procedures for those individuals who had not declined use of their medical records for research at the time their clinical care commenced. A summary of the clinical evaluation process is provided in Appendix A. Donors underwent laparoscopic donor nephrectomy performed by one of a group of three surgeons using the hand-assisted technique (6). For the majority of obese donors, an infra-umbilical midline incision was utilized for the hand-port to facilitate nephrectomy, while non-obese donors had the option of a Pfannenstiel incision.

Based on the information in the medical record, donors were divided into four groups according to BMI: <25 kg/m², 25–29.9 kg/m², 30–34.9 kg/m² and ≥35 kg/m² for analysis. Surgical outcomes including operative time, length of hospital stay (LOS) and perioperative complications were compared across BMI groups. Baseline clinical characteristics recorded at the time of donor evaluation including BMI, blood pressure, fasting plasma glucose, lipid levels, renal function (serum creatinine and glomerular filtration rate by iothalamate clearance), proteinuria and microalbuminuria were compared across BMI groups. For 325 donors with paired pre- and post-donor nephrectomy measurements, blood pressure, fasting plasma glucose, body weight and microalbuminuria at baseline were compared to values at the 6- to 12-month follow-up visits. Prevalence of hypertension, smoking status (non-smoker, or current or any past smoking) and family history of diabetes mellitus or cardiovascular disease was compared across BMI groups. We then compared prevalence rates of these same historical characteristics in donors to renal donor candidates evaluated over this time period who were not approved for donation, using the same BMI defined groups.

We defined perioperative parameters as follows: (i) length of stay—from admission to the hospital on the day of donation to discharge including the operative day; (ii) operative time—time from patient entering the operating room to time to exiting the room including induction of anesthesia, positioning and actual procedure time; (iii) intra-operative complication—an unexpected operative event including conversion to open nephrectomy, unexpected injury to the donor or the donor kidney; (iv) wound infection—wound with purulent drainage that necessitated opening of at least a portion of the incision; (v) wound seroma—non-purulent drainage or aspiration of a subcutaneous fluid collection that was shown to be sterile on subsequent culture; (vi) hernia—fascial defect requiring operative repair; (vii) ileus—lack of bowel function requiring readmission and intravenous fluids and (viii) urinary tract complications—urinary tract infection, testicular pain, epididymitis, urinary retention requiring reinsertion of urethral catheter.

Data were analyzed using JMP 5.1 (SAS Institute) statistical software. Data were expressed as mean ± SEM. Comparisons across multiple BMI groups were performed by ANOVA with specific group comparisons performed using unpaired t-tests. Prevalence rates were compared using chi-square analyses. Pre-operative clinical and laboratory values were compared to post-nephrectomy values using paired t-tests.

Results

Patients

Pre-operative demographic, historical and laboratory baseline data are shown in Table 1 by BMI group. There were 553 renal donors (246 men, 307 women) who underwent laparoscopic donor nephrectomy during the study period; 64% of donors were related to their recipient. Mean age was 42 ± 1 years, 39% were current or former smokers and 21% had previous abdominal surgery. These features did not differ according to BMI. Women outnumbered men twofold in the BMI <25 group (p < 0.01). At higher ranges of BMI, the ratios of men to women were equal. Female donors had lower BMI (27.5 ± 0.3 vs. 28.6 ± 0.3 kg/m², p < 0.05), systolic and diastolic blood pressure (129 ± 1/76 ± 1 vs. 135 ± 1/79 ± 1 mmHg, p < 0.01), fasting plasma glucose (92 ± 1 vs. 97 ± 1 mg/dL, p < 0.01), and serum creatinine (0.97 ± 0.01 vs. 1.18 ± 0.01 mg/dL, p < 0.01), compared to male donors before donor nephrectomy. Similar sex differences were evident after nephrectomy. The prevalence of historical risk factors, including personal history of hypertension, current or former smoking and family history of diabetes or cardiovascular disease did not differ by sex of donor. Lipid profiles indicated a progressive rise in total cholesterol, LDL and triglycerides, and reduced HDL with higher levels of BMI (p < 0.05).

Table 1.  Demographic, historical and laboratory baseline information

BMI group, kg/m^2	<25	25–29.9	30–34.9	≥35
*p < 0.05 versus BMI <25. ^†p < 0.01 versus other BMI groups.
N	170	211	114	58
Age, years	41 ± 1	41 ± 1	43 ± 1	41 ± 1
Mean BMI, kg/m^2	22.4 ± 0.1	27.5 ± 0.1	31.8 ± 0.1	38.7 ± 0.6
Gender (M:F)	53:117^†	109:102	59:54	25:33
Kidney side (L:R)	132:38	162:49	87:27	52:6
Donor type, % LRD	66	64	57	66
Prior abdominal surgery N (%)	37 (22)	44 (21)	25 (22)	12 (21)
Current smoker, %	24	27	19	24
Past smoker, %	22	20	15	22
FH diabetes, %	33	36	42	47
FH CV disease, %	53	49	58	49
History of HTN, %	4	8	7	14
S cholesterol, mg/dL	190 ± 3	195 ± 3	204 ± 4*	204 ± 7*
S triglycerides, mg/dL	106 ± 9	132 ± 6*	154 ± 9*	140 ± 12*
HDL, mg/dL	59 ± 1	51 ± 1*	48 ± 1*	48 ± 2*
LDL, mg/dL	112 ± 3	120 ± 3	126 ± 3*	137 ± 10*

When accepted donors were compared to 207 potential donors who were not approved for donation (Table 2), hypertension was more prevalent in those not approved across all BMI groups (13–40%) with highest rates in those with BMI ≥35 kg/m² (p < 0.01). Exclusion rates were higher for those with BMI ≥35 kg/m² (p < 0.01). Family history of diabetes and cardiovascular disease were higher in not approved individuals with the highest rates (71% with family history of diabetes, 83% with family history of cardiovascular disease, p < 0.05 vs. normal weight) in those with BMI ≥35 kg/m².

Table 2.  Comparison of accepted and denied renal donor candidates

BMI	% denied	Current or past smoking, %		History of HTN, %		FH of DM, %		FH of CV disease, %
		Accepted	Denied	Accepted	Denied	Accepted	Denied	Accepted	Denied
*p < 0.05 versus accepted donors. ^†p < 0.01 versus accepted donors. ^#p < 0.05 between BMI classes. ^‡p < 0.01 between BMI classes.
<25	25	46	56	4	13^†	33	37	53	56
25–29.9	21	47	54	8	33^†	36	46	49	77^†
30–34.9	31	34	54*	7	38^†	42	57 (0.07)	58	70
≥35	41^‡	47	54	14	40^†‡	47	71*^‡	49	83^†#

Intra-operative course

There were no perioperative donor deaths. Intra-operative complications did not differ between BMI groups occurring in 1% of surgeries (Table 3). Conversion to open nephrectomy occurred in 5 of 553 cases (1%) and did not differ with respect to BMI. Conversion to open nephrectomy was associated with surgeon experience, with no conversions occurring in the last 300 cases. The mean operative time ranged from 127 ± 3 min (2 h, 7 min) in patients with BMI <25 kg/m² to 146 ± 6 min (2 h, 26 min) in patients with BMI ≥35 kg/m². While this difference was statistically significant, the actual time difference was only 19 min.

Table 3.  Perioperative morbidity

BMI group, kg/m^2	<25	25–29.9	30–34.9	≥35
Mean ± SEM, *p < 0.05 versus BMI <25. ^†One patient had 2 complications so 12 patients had a total of 13 complications.
N	170	211	114	58
Conversion to open nephrectomy, N	1	2	0	2
Operative time, minutes	127 ± 3	134 ± 2	151 ± 4*	146 ± 6*
LOS, days	2.3 ± 0.1	2.2 ± 0.1	2.2 ± 0.1	2.4 ± 0.1
Perioperative complications, N (%)
Intra-operative	2 (1) 1 bladder injury,	2 (1) 2 conversion	1 (1) 1 vascular	2 (3) 2 conversion
complications N (%)	1 conversion to open	to open	injury to donor	to open
Re-operation	1 (1)	0	0	0
Wound complications	4 (2)	8 (4)	11 (10)*	5 (9)*
1. Wound infection	2 (1)	5 (2)	6 (5)	3 (5)
2. Seroma	1 (1)	1 (0.5)	3 (3)	1 (2)
3. Hernia	1 (1)	2 (1)	2 (2)	1 (2)
Other complications
1. Ileus	0	6 (3)	0	0
2. Urinary tract complications	2 (1)	6 (3)	1 (1)	1 (2)
Other	0	0	1 (1) laryngeal edema	1 (2) stitch granuloma
Total perioperative complications	9 (5)	22 (10)	13 (12)^†	9 (16)*

Early post-operative course

The LOS for the initial hospitalization was similar in the four groups. The only re-operation occurred early in our experience in a non-obese patient. Wound complications (infections, seromas and hernias) were the most frequent procedure-related complications in all groups and increased with increasing donor BMI (2% < 25 kg/m², 4% 25–29.9 kg/m², 10% 30–34.9 kg/m², 9%≥ 35 kg/m², p < 0.05). Wound infections occurred in 5% of obese patients (>30 kg/m²) and in 1–2% of patients with a BMI <30. This difference was not statistically significant. Hernias and seromas occurred in 1–3% of all patients. Other complications such as ileus and urinary tract complications did not differ by donor BMI.

When all procedure-related complications were added together, the patients with a BMI ≥35 kg/m² had a higher complication rate compared to patients with BMI <25 (16% vs. 5%) with wound complications accounting for the majority of the difference. However total perioperative complications for the BMI ≥35 group were not significantly higher compared to the mid-range BMI groups (25–29.9 and 30–34.9 kg/m² groups).

One-year medical follow-up

Clinical characteristics before donor nephrectomy and at 6- to 12-month (mean 11 ± 0.34 months, range 1–49, median 11 months) follow-up for those donors with paired measurements are shown in Table 4. Pre-nephrectomy blood pressures and fasting plasma glucose levels were higher and rose incrementally with BMI (p < 0.05) (Figure 1 and Table 4). Serum creatinine levels did not differ between groups. Direct measurements of iothalamate clearance indicated a rise in absolute GFR with BMI level (Figure 2A). When expressed as GFR/1.73 m² (correction for body surface area), GFR did not differ with BMI.

Table 4.  Comparison of pre-nephrectomy and 1-year follow-up in 325 living donors.

BMI group, kg/m^2	<25	25–29.9	30–34.9	≥35
Mean ± SEM; BP, blood pressure. *p < 0.05 versus BMI <25. ^¶p < 0.05 versus BMI 25–29.9. ^†p < 0.05 versus pre-nephrectomy.
Baseline clinical characteristics
N (% of pre-donor subgroup)	104 (61)	117 (55)	71 (62)	33 (57)
Systolic BP	126 ± 1	130 ± 1*	137 ± 2*^¶	137 ± 3*^¶
Diastolic BP	73 ± 1	77 ± 1*	80 ± 1*	79 ± 2*
S creat, mg/dL	1.03 ± 0.01	1.07 ± 0.02	1.07 ± 0.02	1.07 ± 0.02
Fasting glucose, mg/dL	91 ± 1	94 ± 1*	96 ± 1*	95 ± 2*
24 hr urine microalbumin (mg)	9 ± 1	7 ± 1	8 ± 1	9 ± 2
Post-nephrectomy clinical characteristics (mean 11 ± 0.34 months after nephrectomy)
Weight change, kg	1.6 ± 0.6	0.9 ± 0.5	0.7 ± 1.9	0 ± 1.7
Systolic BP	121 ± 1^†	128 ± 1*^†	136 ± 2*^¶	135 ± 2*^¶
Diastolic BP	71 ± 1^†	75 ± 1*^†	77 ± 1*^†	77 ± 1*
S creat, mg/dL	1.33 ± 0.02	1.39 ± 0.02	1.44 ± 0.03*	1.39 ± 0.04
S glucose, mg/dL	91 ± 1	92 ± 1	96 ± 2*^¶	97 ± 2*^¶
24-hr urine microalbumin (mg)	9 ± 1	7 ± 1	9 ± 2	7 ± 3

Figure 1. Blood pressure measurements at baseline and 6–12 months following donor nephrectomy in 553 renal donors. Subjects were divided into four groups according to body mass index (BMI). Blood pressure was higher for those with BMI 25–29.9 kg/m² and incrementally higher in those with BMI ≥30 kg/m². *p < 0.05 compared to BMI <25; ⁺p < 0.05 compared to BMI 25–29.9, ^†p < 0.05 versus pre-nephrectomy.

Figure 2. Glomerular filtration rate determined by iothalamate renal clearance prior to (A) and 6–12 months following (B) donor nephrectomy. Subjects were divided into four groups according to BMI. Shaded columns indicate uncorrected renal clearance; open bars show renal clearance corrected for body surface area. Absolute GFR rose incrementally with BMI. Once corrected, there were no differences between groups. A similar pattern was observed following nephrectomy. *p < 0.05 compared to BMI <25; ^†p < 0.05 compared to BMI 25–29.9.

Changes in blood pressure and GFR are shown in Figures 1 and 2B; blood pressure values, weight change, serum creatinine and urinary microalbumin after donor nephrectomy are shown in Table 4. Comparable trends of rising blood pressure and absolute GFR by BMI group persisted as before donation, with higher blood pressure associated with higher BMI (p < 0.05). Blood pressure levels were unchanged or reduced following donor nephrectomy, compared to pre-nephrectomy values (p < 0.05). No differences were seen in amount of weight gain by BMI group while there were minor increases in serum creatinine and glucose levels with higher BMI group. Uncorrected GFR was greater with higher BMI after donor nephrectomy (p < 0.05) but did not differ when corrected for size (Figure 2B). There were no differences in microalbuminuria across BMI groups. Microalbumin excretion did not change, despite a reduction in GFR associated with nephrectomy.

Discussion

Our results indicate that otherwise healthy Caucasian renal donors whose BMI extends above 30 kg/m² (classified as obese) and with normal renal function can donate a kidney safely in the short-term. Our selection criteria based upon blood pressure, family history of diabetes and cardiovascular disease led to greater exclusion rates in obese donor candidates. Operative times for laparoscopic donor nephrectomy were longer for obese donors, with higher rates of perioperative complications only in the most obese donors but without difference in LOS. Although considered acceptable, blood pressure, fasting plasma glucose levels and lipid values were higher in donors with BMI ≥30 pre-operatively and remained so 6–12 months after nephrectomy. There were no differences in residual renal function or microalbuminuria across BMI groups.

Existing evidence suggests that people who donated kidneys over the past 50 years have not incurred a significant increase in health risks. Late follow-up series of renal donors report a small increased risk of hypertension or proteinuria after renal donation with maintenance of normal renal function (1,7,8). These reports include primarily donors of normal weight and excellent health. With the increasing success of living donation and the shortage of deceased-donor kidneys, prospective donors are being considered even with isolated medical conditions such as obesity that place them outside what traditionally might be considered ideal donors. We have approached these non-conventional donors using strict selection criteria (absence of albuminuria, normoglycemia, corrected iothalamate clearance >80 mL/min per 1.73 m²), and a requirement for follow-up (currently a mean of 11 months in this study).

Our findings provide new information on several aspects of the donor process: differences in baseline clinical parameters including cardiovascular risk factors, perioperative course, and measurement of renal function 1 year after donation. We noted higher fasting glucose levels and cholesterol measurements with greater BMI even though values were within the normal range. There was a definite trend to higher blood pressure levels with greater BMI. Technical factors may contribute to elevated readings related to arm size and difficulty with blood pressure cuff fit. Once corrected for donor size (using body surface area), renal function as assessed by iothalamate clearance did not differ across BMI groups.

Most of the surgical literature suggests that obese patients have more perioperative complications and a slower recovery rate compared to non-obese patients. The few studies of perioperative complications in obese living kidney donation suggest that from a surgical perspective, kidney donation is safe. Pesavento et al. showed that 107 obese living kidney donors had similar complications to 116 non-obese donors (2). However, in that study the group designated obese included individuals with BMI ≥27 kg/m², some of whom would now be classified as only overweight by World Health Organization definition. Reports by others confirm the safety and feasibility of the laparoscopic technique for all kidney donors including those who are obese (3,5).

In our current study of 553 hand-assisted laparoscopic donor nephrectomies, 172 of whom had a BMI ≥30 kg/m², we found that major surgical complications (conversion to open nephrectomy, re-operations, etc.) were no more common in obese than non-obese donors. Operative time was increased (by a mean of 19 min) and total perioperative complication rate was higher in the highest BMI group compared to BMI <25. Most of this increase was due to wound complications such as infections and seromas. The overall 9–10% wound complication rate for obese patients is a moderate increase over the 2–4% rate in non-obese donors and should be part of the informed consent given to obese donors.

One of the major demonstrated benefits of minimally invasive surgery is a shortened recovery time. Indeed, in our study the post-operative length-of-stay was similar for obese and non-obese donors. Other data such as return to work or return to previous level of functioning were not collected in this study but would be helpful to assess the differential impact of laparoscopic donor nephrectomy by donor BMI. The current study demonstrates a low procedure-related morbidity and good early recovery in obese donors. While the current study does not provide data comparing open to laparoscopic approaches to donation, it is our opinion that the technique of laparoscopic donor nephrectomy results in reduced morbidity in obese patients and has a positive impact on their perioperative outcomes.

At follow-up 1 year after renal donation, obese donors had comparable levels of residual renal function as demonstrated by iothalamate clearance. Measurements of urinary microalbumin were normal at baseline and did not change following donor nephrectomy. Blood pressure was lower overall at the follow-up visit and stable or lower in individual subgroups. It must be emphasized that while these early data are encouraging, this follow-up must be considered short in these donors who are expected to live for decades.

Long-term follow-up of renal donors is limited. This is especially true regarding obese donors, as obesity has been considered a relative exclusion until recently. Anderson et al. reported a 10- to 20-year follow-up on 105 donors (73% response rate) (1). Of the 100 surviving donors, mean serum creatinine was 1.2 mg/dL and mean 24-h urine protein was 89 mg. Hypertension was present in 19%, defined as blood pressure of 160/95 MmHg or higher. Rates of proteinuria were low (13%), only 3 with levels above 500 mg/24 h. The highest level of proteinuria was seen in an obese donor with progressive weight gain raising the possibility that his obesity may have played a role. Reports by others demonstrate rates of hypertension and proteinuria similar to those of the age-matched general population (7,8). Torres et al. reported greater weight gains 10 years after donation in renal donors who were already overweight at the time of donation (9). Weight, age and MAP at donation were predictors of hypertension (160/95 MmHg or on medications) at follow-up. Gracida et al. reported an 80-month follow-up of 628 renal donors, 81 of whom were obese (BMI >30 kg/m²) at the time of donation. While obese donors showed a trend to higher mean arterial pressure and higher unindexed GFR, there were no significant differences from normal donors (10).

Perhaps the greatest risk for renal disease in obese donors is the possibility that they may be at greater risk for developing type II diabetes mellitus later in life. Prevalence rates for diabetes (diagnosed and undiagnosed) range from 2.2% in the second and third decades to 19% at age ≥60 years (11). Risk for diabetes increases approximately two-fold in black and Mexican-Americans. BMI is a strong predictor of diabetes risk, as demonstrated in Caucasian, Hispanic and Pima-Indian populations (12–16). The impact of nephrectomy on the obese individual who subsequently develops diabetes or hypertension is unknown, although hypertension alone in non-obese Caucasian donors rarely leads to renal failure. In long-term (20–37 years) follow-up of 773 living kidney donors, Ramcharan and Matas detected 19 donors who developed diabetes after donation; in six who had follow-up creatinine measurements, only one value was elevated at 2.0 mg/dL and none developed renal failure (7). We pay special attention to fasting glucose levels in our evaluation and require normal urinary microalbumin excretion (<30 mg/24 h). This approach is in agreement with the recommendations of the Expert Committee on the Diagnosis and Classification of Diabetes Mellitus that neither hemoglobin A_1c nor oral glucose tolerance testing (OGTT) provide more sensitive diagnostic capability, related to lack of standardized methodologies, less reproducibility and greater cost (17,18). We exclude donor candidates with impaired glucose tolerance (≥110 mg/dL), for whom OGTT is currently advised. Recent changes in the definition of impaired glucose tolerance (from ≥110 mg/dL to ≥100 mg/dL) may require stricter limits on donor selection but did not utilize either hemoglobin A_1c or OGTT. We depend upon measured renal function by iothalamate clearance rather than calculated GFR and require an iothalamate clearance of greater than 80 mL/min after correction for body surface area to ensure donors have adequate remaining renal function after donor nephrectomy. Family history of diabetes was considered in decision making as reflected by differences in rates between donors accepted and those denied, particularly at the highest levels of BMI (Table 2).

Does obesity by itself constitute an increased risk for developing kidney disease? We believe that the answer to this question is currently unknown. Praga et al. reported that in patients who underwent nephrectomy for medical reasons, proteinuria and/or elevated serum creatinine (mean serum creatinine 3.9 ± 3.2 mg/dL) developed in 92% (12/14) of patients who were obese at the time of nephrectomy compared to 12% of 59 non-obese patients (19,20). The presence of renal disease and co-morbid conditions at the time of nephrectomy was not presented in detail and may not be applicable to donors in the current study. These findings implicate the combination of obesity and reduced number of functioning nephrons after nephrectomy as a high-risk state for the development of proteinuria and renal failure. Proteinuria has been reported with massive obesity, most commonly caused by focal and segmental glomerulosclerosis (FSGS). Additionally, there are reports of a different renal lesion in obese individuals characterized by glomerulomegaly with fewer lesions of segmental sclerosis and less extensive foot process effacement. This entity termed obesity-related glomerulopathy (ORG), was more commonly identified in a large biopsy series, increasing from 0.2% to 2%, a tenfold increase over 15 years (21). Parallel increases in obesity over this time suggest that the prevalence of this disease may continue to increase, yet the true patient population at risk remains poorly characterized. Realizing these concerns, we believe it is reasonable to set a limit on extent of obesity acceptable for our donors until longer follow-up is available. As a conservative measure, we have set an arbitrary limit of BMI <40 kg/m² for acceptance of obese donors in our program.

We observed a surprisingly high rate of current or previous smoking in our living kidney donors at 44%. Smoking rates did not differ by BMI group. Although nearly half (20% of our donors) quit smoking prior to their donor evaluation, 24% were active smokers. Prospective kidney donors are advised to quit smoking by the evaluating nephrologist and transplant-hypertension nurse. We have not refused donation solely on the basis of smoking. More likely current smokers were excluded by reduced GFR, hypertension or other factors as demonstrated by a trend to higher smoking rates in those renal donor candidates denied approval. Known risks of accelerated cardiovascular disease and progression of renal disease related to smoking highlight the need for closer attention to this issue (22,23).

Over the past several years we have accepted select individuals who are obese but otherwise in good health. Our data indicate a spectrum of rising levels of glucose, triglycerides and blood pressure with BMI even while these values remain within normal ranges. More donor candidates were denied approval at higher BMI associated with higher rates of hypertension, and family history of diabetes and cardiovascular disease. Among donors at BMI ≥35 kg/m², only 12 had a BMI above 40 (21% of highest BMI group, 2% of total group) including 3 above 45. Our study presents initial data in selected patients across a wide range of BMI and provides a foundation to establish long-term follow-up of these individuals. These results are unique in that we add a standard return visit at 6–12 months after renal donation providing at least early follow-up including blood pressure, urinary microalbumin and GFR on large numbers of renal donors. This information extends our knowledge beyond the immediate perioperative and post-operative period with demonstrated clinical stability. We believe we have an obligation to closely monitor those wishing to donate at higher risk. For obese donors, follow-up provides the potential for intervention utilizing dietary, exercise and mental health expertise.

Our results support the cautious acceptance of obese donors who meet strict selection criteria and who are highly motivated to donate. The decision to donate a kidney to a family member or friend is an altruistic action, which may lead to improved quality of life for both recipient and donor. While our results regarding the safety of accepting obese individuals as live donors are encouraging, we must re-emphasize that these results involve only short-term follow-up in what we consider a highly select group of obese donors. Within our program, we have arbitrarily set an upper limit on BMI for donor acceptance. We advocate the continued careful study of obese donors and do not support their widespread use until longer follow-up is available.

Appendix

Appendix A:

As part of the clinical practice of the transplant program, a nephrologist and a transplant surgeon independent of the recipient's transplant team evaluated each patient prior to acceptance as a renal donor. Routine donor evaluation included blood pressure measurements (oscillometric recorder, Dinamap; Critikon, Tampa, FL, USA), physical examination, laboratory testing including fasting plasma glucose, lipid profile, serum creatinine, urinalysis and glomerular filtration rate by iothalamate clearance, and renal imaging by computed tomography angiography. Additional studies were performed as needed including cardiac evaluation for those at increased risk by age or the presence of risk factors and cancer screening according to gender, age or family history. Exclusion criteria for donation included age less than 18 years, fasting hyperglycemia (fasting plasma glucose ≥110 mg/dL), evidence for renal disease including microalbuminuria or proteinuria above normal threshold levels, significant cardiac disease, viral hepatitis, malignancy, untreated substance abuse and psychiatric illness. Hypertension was a relative exclusion, except in select cases where blood pressure was easily controlled with one or two agents. ^APrevious abdominal surgery was not a contra-indication to laparoscopic nephrectomy. Renal donors were asked to return for follow-up measurements of blood pressure, fasting plasma glucose, serum creatinine and glomerular filtration rate 6–12 months after nephrectomy.

^ATextor SC, Taler SJ, Driscoll N, Larson TS, Gloor J, Griffin M et al. Blood pressure and renal function after kidney donation from hypertensive living donors. Transplantation 2004; 78: 276–282.