Compensatory hypertrophy of the remaining kidney in medically complex living kidney donors over the long term

Renal transplants increase in size and function in keeping with compensatory renal hypertrophy

AIM

To evaluate changes in allograft kidney length in renal transplant recipients and the relationship with estimated glomerular filtration rate (eGFR).

METHODS

This single-centre retrospective study of renal transplant recipients was conducted at Flinders Medical Centre (FMC) from January 2007 to June 2020. Donor and recipient details, renal allograft length from transplant ultrasounds at 0, 1, 3, 6 and 12 months were collected. The association between compensatory renal hypertrophy (CRH) and eGFR and its magnitude was analysed using multivariate multilevel mixed-effects linear regression models.

RESULTS

A total of 183 renal transplant recipients were studied. 100 of 175 recipients (62.9%) demonstrated an increase in renal length defined as any increase in maximal longitudinal diameter on serial ultrasounds. Twenty-three recipients (13.1%) had no change in transplant length and 42 recipients (24%) had a decrease in length. The mean increase in kidney length over the first 12 months was 0.57 cm. Ninety of 156 (57.7%) recipients with a renal ultrasound within a month post-transplant demonstrated a mean increase kidney length of 0.3 cm. Multivariate analysis demonstrated that eGFR increased by 2.5 mL/min/1.73 m2 (95% CI 0.72- 4.4; p = .006) with every 1 cm increase in kidney length. Absolute changes in kidney length did not demonstrate any statistically significant correlation with eGFR in both complete case and multiple imputation analysis.

CONCLUSION

An increase in transplant kidney length is common in renal transplant recipients and is associated with enhanced eGFR. However, further studies need to be performed to study the association of absolute change in kidney length and eGFR.

Comparison of CT volumetry versus nuclear renography for predicting remaining kidney function after uninephrectomy in living kidney donors

Computed tomography (CT) and nuclear renography are used to determine kidney procurement in living kidney donors (LKDs). The present study investigated which modality better predicts kidney function after donation. This study included 835 LKDs and they were divided into two subgroups based on whether the left–right dominance of kidney volume was concordant with kidney function (concordant group) or not (discordant group). The predictive value for post-donation kidney function between the two imaging modalities was compared at 1 month, 6 months, and > 1 year in total cohort, concordant, and discordant groups. Split kidney function (SKF) measured by both modalities showed significant correlation with each other at baseline. SKFs of remaining kidney measured using both modalities before donation showed significant correlation with eGFR (estimated glomerular filtration rate) after donation in the total cohort group and two subgroups, respectively. CT volumetry was superior to nuclear renography for predicting post-donation kidney function in the total cohort group and both subgroups. In the discordant subgroup, a higher tendency of kidney function recovery was observed when kidney procurement was determined based on CT volumetry. In conclusion, CT volumetry is preferred when determining procurement strategy especially when discordance is found between the two imaging modalities.

Practice Patterns in the Acceptance of Medically Complex Living Kidney Donors with Obesity, Hypertension, Family History of Kidney Disease, or Donor-Recipient Age Discrepancy

Background  To assess the practice patterns of the acceptance of medically complex living kidney donors (MCLKDs).

Methods  We distributed a survey to nephrologists and transplant surgeons (TS) across the world through major international transplant societies. The survey contained questions regarding obesity, abnormal blood glucose profile, mild hypertension, donor-recipient age discrepancy, or family history of kidney disease of unknown etiology.

Results  In total, 239 respondents from 29 countries (42% were nephrologists and 58% were TS).

Most respondents would allow donations from obese donors, especially if they intended to lose weight but would be cautious if these donors had abnormal blood glucose or family history of diabetes mellitus. In hypertensive donors, future pregnancy plans mattered in decisions regarding the acceptance of female donors. Most respondents would allow young donors but would be more cautious if they had a future risk of hypertension or a family history of kidney disease of unknown etiology. They would also allow donations from an older person if prolonged waiting time was anticipated. We found multiple areas of consensus of practice among the diverse members of international transplant societies, with some interesting variations among nephrologists and TS.

Conclusions  This survey highlights the practice patterns of the acceptance of MCLKDs among the international community. In the absence of clear guidelines, this survey provides additional information to counsel kidney donors with these conditions.

Evaluation of functional outcome of bilateral kidney tumors after sequential surgery

Background

There are limited data concerning patients treated with sequential bilateral kidney surgery. Current guidelines still lack an optimal surgical sequencing approach. We evaluated renal functional outcomes after sequential partial nephrectomy (PN) and radical nephrectomy (RN) in patients with bilateral renal cell carcinoma (RCC).

Methods

A propensity score matched cohort of 267 patients (synchronous bilateral RCCs, N = 44 [88 lesions]; metachronous bilateral, N = 45 [90 lesions]; unilateral, N = 178) from two tertiary institutions were retrospectively analyzed. Synchronous bilateral RCCs were defined as diagnosis concomitantly or within 3 months of former tumor. Renal functional outcomes were defined as estimated glomerular filtration rate (eGFR) changes and de novo chronic kidney disease (CKD, stage ≥3) after surgery. Renal functional outcomes and clinical factors predicting de novo CKD were assessed using descriptive statistics and Cox regression analysis.

Results

In subgroup of bilateral RCCs, patients underwent sequential PN (N = 48), PN followed by RN (N = 8), or RN followed by PN (N = 25). Final postoperative estimated glomerular filtration rates (eGFRs) were 79.4, 41.4, and 61.2 ml/minute/1.73 m2, respectively (p = 0.003). There were significant differences in eGFR decline from baseline and de novo chronic kidney disease (CKD stage ≥ III) among groups, with PN followed by RN group showing the worst functional outcomes (all p <  0.05). Moreover, sequential PN subgroup in bilateral RCC showed significantly higher rate of de novo CKD than unilateral RCC group (13.8% vs. 6.9%, p = 0.016). On multivariate analysis, hypertension (p = 0.010) and surgery sequence (PN followed by RN, p <  0.001) were significant predictors of de novo CKD.

Conclusions

The surgery sequence should be prudently determined in bilateral renal tumors. PN followed by RN showed a negative impact on renal functional preservation. Nephron-sparing surgery should be considered for all amenable bilateral RCCs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08324-3.

Post-kidney donation glomerular filtration rate measurement and estimation

BACKGROUND

Long-term consequences associated with kidney donation are controversial. Pre- and post-donation glomerular filtration rates (GFRs) are determinants of renal and cardiovascular risk weighting. In Latin America, there is limited experience in evaluating kidney function using GFR measurement techniques in kidney donors. The MDRD 4-variable and CKD-EPI equations are considered reasonable options. The objective of this study was to evaluate the performance of the MDRD and CKD-EPI equations in post-nephrectomy GFR dynamics in kidney donors.

MATERIALS AND METHODS

A prospective cohort study with GFR measurement and estimation in 189 kidney donors who underwent nephrectomy between 2007 and 2016 at the Hospital Privado Universitario de Córdoba [Private University Hospital of Córdoba] in Córdoba, Argentina. GFRs were evaluated before and after nephrectomy by iothalamate clearance determined by HPLC and by the MDRD and CKD-EPI equations for estimating GFR. Two groups were formed for this study: Group 1 (n=107), with an evaluation time subsequent to GFR stabilization (3 months) of up to 5 years, and Group 2 (n=82), with an evaluation time of 5-10 years following donation. Measured GFR (mGFR) was assessed by iothalamate clearance determined by HPLC.

RESULTS

Renal compensation values were 61.9% (52.0%-71.1%) and 75.6% (64.9%-84.4%) for Group 1 (n=107) and Group 2 (n=82), respectively. MDRD underestimated the GFR in 3.2% (90ml/min/1.73m²) and 38.6% (60ml/min/1.73m²) compared to the mGFR, and CKD-EPI underestimated the GFR in 2.6% (90ml/min/1.73m²) and 13.8% (60ml/min/1.73m²). Diagnostic performance was evaluated with a ROC curve (mGFR<60ml/min/1.73m²) for MDRD (ABC=0.66; CI: 0.59-0.73; sensitivity: 98.7%; specificity: 63.3%) and for CKD-EPI (ABC=0.79 CI: 0.73-0.85; sensitivity: 96.9%; specificity: 76.4%. Estimated GFR (eGFR) showed poor performance for estimating the glomerular filtration rate in the post-nephrectomy follow-up of donors over 50 years of age.

CONCLUSIONS

Equations for estimating GFRs showed poor performance for long-term follow-up of post-nephrectomy GFRs. Measuring GFRs to determine kidney function is recommended in the screening and follow-up of some donors under the current selection criteria.

The importance of kidney volume as a marker in the assessment of living-donor kidney transplantation in Japan

BACKGROUND

In living kidney transplantation, predicting the risk of end-stage kidney disease in the organ donors though crucial remains to be resolved. Thus, any useful biomarker to predict kidney outcome would be highly desirable to safeguard donors.

METHODS

This retrospective study was conducted at Nagoya Daini Red Cross Hospital to confirm whether an increase in preserved kidney volume (PKV) was a predict marker of proteinuria. A change of PKV before and 1 year after kidney donation was measured, and its association with proteinuria 3 years after the donation was analyzed.

RESULTS

A total of 119 kidney donors who met the Japanese donor guideline were enrolled. The mean age was 57.4 years, 46.2% were male. The mean values of the variables before kidney donation (baseline) were: BMI levels: 23.4 kg/m², BSA-adjusted PKV: 132.9 cm³/1.73 m², and estimated glomerular filtration rate (eGFRave): 82.9 mL/min/1.73 m². A positive correlation was noted between BSA-adjusted PKV and eGFRave (r = 0.61, p < 0.001). BSA-adjusted PKV increased by 19.5% 1 year after donation, and the median urine protein was 0.04 g/gCre. Linear regression analyses showed that change of PKV and BSA-adjusted PKV before the donation were significantly associated with proteinuria 3 years after donation.

CONCLUSION

Change of PKV and BSA-adjusted PKV before donation is important factors for proteinuria after donation under the Japanese donor guidelines. Further studies are needed to confirm whether these factors are associated with renal survival after donation.

The Biology of Physiological Health

The ability to maintain health, or recover to a healthy state after disease, is an active process involving distinct adaptation mechanisms coordinating interactions between all physiological systems of an organism. Studies over the past several decades have assumed the mechanisms of health and disease are essentially inter-changeable, focusing on the elucidation of the mechanisms of disease pathogenesis to enhance health, treat disease, and increase healthspan. Here, I propose that the evolved mechanisms of health are distinct from disease pathogenesis mechanisms and suggest that we develop an understanding of the biology of physiological health. In this Perspective, I provide a definition of, a conceptual framework for, and proposed mechanisms of physiological health to complement our understanding of disease and its treatment.

How Does the Remaining Single Kidney Cope After Contralateral Nephrectomy of the Kidney Donor? A Single-Center Cohort Study

Introduction

Immediately after kidney donation, the remaining kidney will undergo hyperfiltration and work at a higher level to compensate for the other kidney's loss. It is estimated that 70% of the baseline renal function before the donation is recovered post-donation. However, factors that determine the post-donation renal compensation are not well understood.

Methods

We conducted a retrospective study of 190 consecutive kidney donors who completed a one-year follow-up in order to predict the factors affecting the function of the remaining kidney post-contralateral nephrectomy.

Results

We enrolled 190 living kidney donors who had completed at least one year of follow-up after nephrectomy. Among the participants, 149 (78.4%) were males and 41 (21.6%) were females. The mean age of the participants was 31.33 ±7.9 years and the mean body mass index (BMI) was 25.6 ±3.9 kg/m². Before kidney donation, the mean estimated glomerular filtration rate (eGFR) and serum creatinine were 114.31 ±15.94 ml/min/1.73 m² and 71.60 ±10.62 mmol/min, respectively. At the one-year follow-up, the mean eGFR was 77.97 ±14.44 ml/min/1.73 m² and serum creatinine was 100.84 ±20.15 mmol/min. The female gender [odds ratio (OR): 20.6, 95% CI: 3.9-107.7, p: <0.001] and having a higher baseline eGFR (OR: 8.8, 95% CI: 1.6-45.8, p = 0.01) were found to be significant predictors of having a better eGFR at one year post-nephrectomy.

Conclusions

Female gender and pre-donation low serum creatinine and high eGFR were the significant predictors of better kidney function at one year post-contralateral nephrectomy. However, further studies with longer follow-up durations are needed to better assess the factors that could predict renal compensation and the renal compensation rate's suitability as a prognostic measure for long-term renal outcomes.

Clinical outcomes in donors and recipients of kidney transplantations involving medically complex living donors - a retrospective study

We retrospectively compared the post-transplantation graft survival and the donor's estimated glomerular filtration rates (eGFRs) following living donor kidney transplantations (LDKTs) involving medically complex living donors (MCLDs) (the elderly and patients with obesity, hypertension, diabetes mellitus, or reduced renal function) and standard living donors (SLDs). The clinical data on patients who underwent LDKTs at our institution from 2006-2019, including 192 SLDs and 99 MCLDs, were evaluated. Regarding recipients, the log-rank test and multivariable Cox proportional hazards analyses showed a higher incidence of overall and death-censored graft loss in the recipients who received kidneys from MCLDs (Hazard ratio = 2.16 and 3.25, P = 0.015 and 0.004, respectively), after adjusting for recipient-related variables including age, sex, duration of dialysis, ABO compatibility, and donor-specific antibody positivity. Regarding donors, a linear mixed model showed significantly lower postdonation eGFRs (-2.25 ml/min/1.73 m² , P = 0.048) at baseline in MCLDs than SLDs, but comparable change (difference = 0.01 ml/min/1.73 m² /year, P = 0.97). In conclusion, although kidneys from MCLDs are associated with impaired graft survival, the donation did not adversely affect the MCLDs' renal health in at least the short-term. LDKTs involving carefully selected MCLDs would be an acceptable alternative for recipients with no SLDs.

Remaining kidney volume indexed to weight as a strong predictor of estimated glomerular filtration rate at 1 year and mid-term renal function after living-donor nephrectomy - a retrospective observational study

The donors' estimated glomerular filtration rate (eGFR) after living nephrectomy has been a concern, particularly in donors with smaller kindeys. Therefore, we developed this retrospective observational study in 195 donors to determine the ability remaining kidney volume indexed to weight (RKV/W) to predict eGFR at 1 year through multivariate linear regression and to explore this relationship between annual eGFR change from 1 to 4 years postdonation evaluated by a linear mixed model. Comparing RKV/W tertiles (T1, T2, T3), RKV/W was a good predictor of 1-year eGFR which was significantly better in T3 donors. Gender, predonation eGFR, and RKV/W were independent predictors of eGFR at 1-year. In a subgroup with predonation eGFR < 90mL/min/1.73 m² , a significant prediction of eGFR < 60mL/min/1.73 m² was detected in males with RKV/W ≤ 2.51cm³ /kg. Annual eGFR (ml/min/year) change from 1 to 4 years was + 0.77. RKV/W divided by tertiles (T1-T3) was the only significant predictor: T2 and T3 donors had an annual eGFR improvement opposing to T1. RKV/W was a good predictor of eGFR at 1 year, independently from predonation eGFR. A higher RKV/W was associated with improved eGFR at 1 year. A decline in eGFR on the four years after surgery was only noticeable in donors with RKV/W ≤ 2.13cm³ /kg.

The contralateral kidney presents with impaired mitochondrial functions and disrupted redox homeostasis after 14 days of unilateral ureteral obstruction in mice

In unilateral ureteral obstruction (UUO), both oxidative stress and mitochondrial dysfunction are related to cell death. The aim of this study has been to characterize profiles of enzyme antioxidant activities and mitochondrial functioning of the contralateral (CL) compared to UUO and Sham (false-operated) kidneys of Balb/c mice. Kidneys were resected 14 days after obstruction for immunohistochemical and cortical mitochondrial functioning assays. Antioxidant enzymes activities were investigated in mitochondria and cytosol. Oxygen consumption (QO₂) and formation of O₂ reactive species (ROS) were assessed with pyruvate plus malate or succinate as the respiratory substrates. QO₂ decreased in CL and UUO in all states using substrates for complex II, whereas it was affected only in UUO when substrates for complex I were used. Progressive decrease in mitochondrial ROS formation–in the forward and reverse pathway at complex I–correlates well with the inhibition of QO₂ and, therefore, with decreased electron transfer at the level of complexes upstream of cytochrome c oxidase. CL and UUO transmembrane potential responses to ADP were impaired with succinate. Intense Ca²⁺-induced swelling was elicited in CL and UUO mitochondria. Important and selective differences exist in CL antioxidant enzymes with respect to either Sham or UUO kidneys: CL kidneys had increased mitochondrial glutathione peroxidase and cytosolic catalase activities, indicative of compensatory responses in the face of an early altered ROS homeostasis (as detected by 4-hydroxynonenal), and of a significant tendency to apoptosis. In CL and UUO, upregulation of nuclear (erythroid-derived 2)-like 2 transcription factor (Nrf2), as well as of cytoplasmic and nuclear Kelch-like ECH-associated protein 1 (Keap1) in opposition to decreased heme oxygenase-1 (HO-1), suggest impairment of the Nrf2/Keap1/HO-1 system. It is concluded that chronic obstruction impairs mitochondrial function in CL and UUO, preferentially affecting complex II.

Creatine is a Conditionally Essential Nutrient in Chronic Kidney Disease: A Hypothesis and Narrative Literature Review

To accommodate the loss of the plethora of functions of the kidneys, patients with chronic kidney disease require many dietary adjustments, including restrictions on the intake of protein, phosphorus, sodium and potassium. Plant-based foods are increasingly recommended as these foods contain smaller amounts of saturated fatty acids, protein and absorbable phosphorus than meat, generate less acid and are rich in fibers, polyunsaturated fatty acids, magnesium and potassium. Unfortunately, these dietary recommendations cannot prevent the occurrence of many symptoms, which typically include fatigue, impaired cognition, myalgia, muscle weakness, and muscle wasting. One threat coming with the recommendation of low-protein diets in patients with non-dialysis-dependent chronic kidney disease (CKD) and with high-protein diets in patients with dialysis-dependent CKD, particularly with current recommendations towards proteins coming from plant-based sources, is that of creatine deficiency. Creatine is an essential contributor in cellular energy homeostasis, yet on a daily basis 1.6–1.7% of the total creatine pool is degraded. As the average omnivorous diet cannot fully compensate for these losses, the endogenous synthesis of creatine is required for continuous replenishment. Endogenous creatine synthesis involves two enzymatic steps, of which the first step is a metabolic function of the kidney facilitated by the enzyme arginine:glycine amidinotransferase (AGAT). Recent findings strongly suggest that the capacity of renal AGAT, and thus endogenous creatine production, progressively decreases with the increasing degree of CKD, to become absent or virtually absent in dialysis patients. We hypothesize that with increasing degree of CKD, creatine coming from meat and dairy in food increasingly becomes an essential nutrient. This phenomenon will likely be present in patients with CKD stages 3, 4 and 5, but will likely be most pronouncedly present in patients with dialysis-dependent CKD, because of the combination of lowest endogenous production of creatine and unopposed losses of creatine into the dialysate. It is likely that these increased demands for dietary creatine are not sufficiently met. The result of which, may be a creatine deficiency with important contributions to the sarcopenia, fatigue, impaired quality of life, impaired cognition, and premature mortality seen in CKD.

Baseline living-donor kidney volume and function associate with 1-year post-nephrectomy kidney function

Living donors may develop kidney dysfunction more often than equally healthy populations. The purpose of this study was to determine whether computed tomography‐assessed remaining kidney volume indexed to body surface area (RKV/BSA) was associated with 1‐year post‐nephrectomy renal function independent of baseline renal function. Using multivariable regression, we modeled 1‐year estimated glomerular filtration rate (eGFR) and eGFR <60 mL /min/1.73 m² and considered pre‐determined baseline eGFR subgroups in 151 consecutive donors. Mean ± SD baseline age, eGFR, RKV, BSA, and RKV/BSA were 38 ± 11 years, 97 ± 16 mL/min/1.73 m², 153 ± 29 mL, 1.9 ± 0.2 m², and 80.0 ± 12.8 ml/m², respectively; 50% were female and 94% were white. Mean baseline eGFR was greater with increasing RKV/BSA tertiles (92 ± 14, 97 ± 16, 107 ± 16 mL/min/1.73 m²; P < 0.001). Post‐nephrectomy eGFR remained separated by RKV/BSA tertiles. At baseline, each SD greater RKV/BSA and eGFR was independently associated with higher adjusted 1‐year eGFR by 2.4 and 9.2 mL/min/1.73 m². Each SD greater age associated with 2.2 mL/min/1.73 m² lower adjusted 1‐year eGFR. Adjusted odds of 1‐year eGFR <60 increased significantly for donors with RKV/BSA <80 mL/m². With baseline eGFR <90, probability of 1‐year eGFR <60 increased to >80% with decreasing RKV/BSA values below 80 mL/m². Those with baseline eGFR >100 rarely developed 1‐year eGFR <60 if RKV/BSA remained >60 mL/m². RKV/BSA independently associated with 1‐year eGFR <60, especially with lower baseline eGFRs. Additional studies should evaluate the predictive utility of this measure and its potential role in donor evaluations and informed consent.

Pre-donation BMI and preserved kidney volume can predict the cohort with unfavorable renal functional compensation at 1-year after kidney donation

BACKGROUND

The magnitude of renal function recovery after kidney donation differs in donors with a heterogeneous background. Preoperative assessment of candidates with potentially unfavorable renal functional compensation is critical when baseline kidney function is marginal. We explored the significance of preserved kidney volume (PKV) and known preoperative risk factors for the prediction of unfavorable renal function compensation.

METHODS

We enrolled 101 living donors for whom a 1-mm sliced enhanced computed tomography scan was performed preoperatively and clinical data could be collected up to 1 year after donation. The donors whose estimated glomerular filtration rate (eGFR) at 1 year after donation was 70% or higher of baseline eGFR were assigned to the "favorable renal compensation" group and the others to the "unfavorable renal compensation" group.

RESULTS

Age, sex, and preoperative serum uric acid level were not significant predictors for "unfavorable renal compensation." Multivariable logistic regression analysis revealed that body mass index (BMI) and body surface area (BSA)-adjusted PKV were independent preoperative risk factors for "unfavorable renal compensation" (adjusted odds ratio, 1.342 and 0.929, respectively). Hypertension and preoperative eGFR were not independent predictors when adjusted with BMI and BSA-adjusted PKV. Receiver operative characteristic analysis revealed that the predictive equation with the two independent predictors yielded a good accuracy to detect donor candidates with unfavorable renal functional compensation (area under the curve = 0.803), and the optimal cut-off values were identified as 23.4 kg/m² for BMI and 107.3 cm³/m² for BSA-adjusted PKV.

CONCLUSIONS

BMI and BSA-adjusted PKV may be useful to select candidates with potentially unfavorable renal function compensation before kidney donation.

Living donor postnephrectomy kidney function and recipient graft loss: A dose-response relationship

Development of end-stage renal disease (ESRD) in living kidney donors is associated with increased graft loss in the recipients of their kidneys. Our goal was to investigate if this relationship was reflected at an earlier stage postdonation, possibly early enough for recipient risk prediction based on donor response to nephrectomy. Using national registry data, we studied 29 464 recipients and their donors from 2008-2016 to determine the association between donor 6-month postnephrectomy estimated GFR (eGFR) and recipient death-censored graft failure (DCGF). We explored donor BMI as an effect modifier, given the association between obesity and hyperfiltration. On average, risk of DCGF increased with each 10 mL/min decrement in postdonation eGFR (adjusted hazard ratio [aHR] 1.06, 95% confidence interval [CI] 1.02-1.10, P = .007). The association was attenuated with higher donor BMI (interaction P = .049): recipients from donors with BMI = 20 (aHR 1.12, 95% CI 1.04-1.19, P = .002) and BMI = 25 (aHR 1.07, 95% CI 1.03-1.12, P = .001) had a higher risk of DCGF with each 10 mL/min decrement in postdonation eGFR, whereas recipients from donors with BMI = 30 and BMI = 35 did not have a higher risk. The relationship between postdonation eGFR, donor BMI, and recipient graft loss can inform counseling and management of living donor kidney transplant recipients.

Effect of unilateral nephrectomy on urinary angiotensinogen levels in living kidney donors: 1 year follow-up study

Background:

Urinary angiotensinogen (uAGT) has recently been proposed as a marker of kidney injury and activated intrarenal renin–angiotensin system. We investigated the effects of living donor nephrectomy on uAGT levels, blood pressure, estimated glomerular filtration rate, proteinuria and compensatory hypertrophy in the remaining kidney of living kidney donors.

Methods:

Twenty living kidney donors were included in the study and followed for 1 year. uAGT levels were measured with enzyme-linked immunosorbent assay preoperatively and postoperatively at the 15th day, 1, 6 and 12 months.

Results:

Four donors were excluded from the study due to lack of data. The mean baseline estimated glomerular filtration rate was 98 ± 15 ml/min/1.73 m². Serum creatinine, uAGT/creatinine, uAGT/protein levels were higher and estimated glomerular filtration rate was lower than baseline values at all time periods. Urinary protein/creatinine levels increased after donor nephrectomy, but after 6 months they returned to baseline values. Renal volume increased after nephrectomy, but these changes did not show any correlation with uAGT/creatinine, uAGT/protein, estimated glomerular filtration rate or systolic/diastolic blood pressures. uAGT/creatinine at 6 months and urinary protein/creatinine ratio at 12 months showed a positive correlation (P=0.008, r=0.639).

Conclusion:

After donor nephrectomy, increasing uAGT levels can be the result of activation of the intrarenal renin–angiotensin system affecting the compensatory changes in the remaining kidney. The long-term effects of increased uAGT levels on the remaining kidney should be examined more closely in future studies.

Postdonation Anemia in Living Kidney Donors

BACKGROUND

The effect of nephrectomy on development of anemia in living kidney donation has not been well studied. We hypothesized that the remaining kidney volume and function after donation are determinants of hemoglobin (Hb) concentration and postdonation anemia (PDA).

METHODS

We studied 398 living kidney donors (LKDs) who donated from January 2001 to December 2013. Demographic variables, hematologic variables, renal mass, and renal function were investigated as factors associated with PDA with the use of univariate and multivariable logistical regression analysis. Renal mass was determined from kidney volume measured with the use of computerized tomographic scans.

RESULTS

Prevalence of PDA in LKDs was 11.8% at a median follow-up time of 601 days. In univariate analyses, PDA was more prevalent in women than in men (72% vs 28%; P = .048). Age and race were not associated factors. Kidney volume was lower in donors with PDA than in those without PDA (326 ± 52 mL vs 368 ± 70 mL; P < .001). Donors with and without PDA had similar predonation and postdonation glomerular filtration rates. In the multivariable logistic regression analysis, total kidney volume and predonation anemia remained as independent factors associated with PDA.

CONCLUSIONS

PDA is prevalent after living kidney donation, with donor kidney volume and predonation hemoglobin levels being independent determinants for PDA.

Compensatory Structural and Functional Adaptation After Nephrectomy in Obese Patients According to Waist Circumference

OBJECTIVE

To investigate whether the postnephrectomy renal adaptation mechanism, focused on functional hyperfiltration as well as structural hypertrophy, was affected by abdominal obesity.

MATERIALS AND METHODS

We retrospectively evaluated 358 patients who underwent simple or radical nephrectomy and nephroureterectomy between 2009 and 2013. Patients were classified according to waist circumference (WC), with values >102 cm in men and >88 cm in women considered high (obesity). Functional renal volume (FRV) was measured using computed tomography performed preoperatively and 6 months postoperatively to evaluate the degree of remnant kidney hypertrophy. The degree of hyperfiltration was calculated from the difference between the preoperative and postoperative glomerular filtration rate (GFR)/FRV.

RESULTS

The mean preoperative GFR, FRV, and GFR/FRV were 72.1 mL/min/1.73 m², 282.8 cm³, and 0.25 mL/min/1.73 m²/cm³, respectively. The percent GFR reduction was significantly greater in the high WC group (high, 25.9% vs normal, 16.0%, P = .036), although the degree of hypertrophic volume in the remnant kidney showed no difference. The change in GFR/FRV was statistically lower in the high WC group (high, 25.7% vs normal, 40.2%, P = .009). The factors associated with postoperative increased GFR/FRV were low preoperative GFR, proteinuria, high predictive preserved functional parenchymal volume ratio, absence of hypertension, increased levels of high-density lipoprotein cholesterol, and normal WC (all P < .05).

CONCLUSION

Patients with high WC might have a large reduction in postoperative renal function, owing to a lower degree of functional hyperfiltration.

Acceptability of older adults as living kidney donors

PURPOSE OF REVIEW

Kidney transplantation from a living kidney donor (LKD) is associated with better long-term survival and quality of life for a patient with end-stage renal disease (ESRD) than dialysis. We reviewed recent literature on the acceptability and outcomes of older adults as LKDs, which may be misunderstood in routine care.

RECENT FINDINGS

Studies report that receiving a kidney from an older LKD is associated with worse recipient and graft survival compared with receiving a kidney from a younger LKD, but similar recipient and graft survival to receiving a kidney from a standard criteria deceased donor. A kidney from a younger vs. older LKD results in better graft survival in younger recipients, whereas the graft survival is similar in older recipients. Compared with healthy matched nondonors, older LKDs have a similar risk of death and cardiovascular disease and the absolute risk of ESRD after 15 years remains less than 1%. The estimated predonation and postdonation lifetime risk of ESRD varies by age, sex and race with lower incidences in individuals who are older, female and white (vs. African-American).

SUMMARY

Donor and recipient outcomes from several studies support the acceptability of older adults as LKDs.

Does size matter? Kidney transplant donor size determines kidney function among living donors

BACKGROUND

Kidney donor outcomes are gaining attention, particularly as donor eligibility criteria continue to expand. Kidney size, a useful predictor of recipient kidney function, also likely correlates with donor outcomes. Although donor evaluation includes donor kidney size measurements, the association between kidney size and outcomes are poorly defined.

METHODS

We examined the relationship between kidney size (body surface area-adjusted total volume, cortical volume and length) and renal outcomes (post-operative recovery and longer-term kidney function) among 85 kidney donors using general linear models and time-to-chronic kidney disease data.

RESULTS

Donors with the largest adjusted cortical volume were more likely to achieve an estimated glomerular filtration rate (eGFR) ≥60 mL/min/1.73 m2 over a median 24-month follow-up than those with smaller cortical volumes (P <0.001), had a shorter duration of renal recovery (1.3-2.2 versus 32.5 days) and started with a higher eGFR at pre-donation (107-110 versus 91 mL/min/1.73 m2) and immediately post-nephrectomy (∼63 versus 50-51 mL/min/1.73 m2). Similar findings were seen with adjusted total volume and length.

CONCLUSIONS

Larger kidney donors were more likely to achieve an eGFR ≥60 mL/min/1.73 m2 with renal recovery over a shorter duration due to higher pre-donation and initial post-nephrectomy eGFRs.

Glomerular Function and Structure in Living Donors: Lessons from Single Nephron Studies

One third of the kidney transplants performed in the USA come from living kidney donors. The long-term outcome of healthy individuals who donate kidneys is mostly excellent, although recent studies have suggested that living donation is associated with a small absolute increase in the risk of end stage renal failure. Much of our understanding about the progression of kidney disease comes from experimental models of nephron loss. For this reason, living kidney donation has long been of great interest to renal physiologists. This review will summarize the determinants of glomerular filtration and the physiology that underlies post-donation hyperfiltration. We describe the 'remnant kidney' model of kidney disease and the reasons why such progressive kidney disease very rarely ensues in healthy humans following uninephrectomy. We also review some of the methods used to determine glomerular number and size and outline their associations.

Differences in GFR and Tissue Oxygenation, and Interactions between Stenotic and Contralateral Kidneys in Unilateral Atherosclerotic Renovascular Disease

BACKGROUND AND OBJECTIVES

Atherosclerotic renal artery stenosis (ARAS) can reduce renal blood flow, tissue oxygenation, and GFR. In this study, we sought to examine associations between renal hemodynamics and tissue oxygenation with single-kidney function, pressor hormones, and inflammatory biomarkers in patients with unilateral ARAS undergoing medical therapy alone or stent revascularization.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Nonrandomized inpatient studies were performed in patients with unilateral ARAS (>60% occlusion) before and 3 months after revascularization (n=10) or medical therapy (n=20) or patients with essential hypertension (n=32) under identical conditions. The primary study outcome was change in single-kidney GFR. Individual kidney hemodynamics and volume were measured using multidetector computed tomography. Tissue oxygenation (using R(2)* as a measure of deoxyhemoglobin) was determined by blood oxygen level-dependent magnetic resonance imaging at 3 T. Renal vein neutrophil gelatinase-associated lipocalin (NGAL), monocyte chemoattractant protein-1 (MCP-1), and plasma renin activity were measured.

RESULTS

Total GFR did not change over 3 months in either group, but the stenotic kidney (STK) GFR rose over time in the stent compared with the medical group (+2.2[-1.8 to 10.5] versus -5.3[-7.3 to -0.3] ml/min; P=0.03). Contralateral kidney (CLK) GFR declined in the stent group (43.6±19.7 to 36.6±19.5 ml/min; P=0.03). Fractional tissue hypoxia fell in the STK (fraction R(2)* >30/s: 22.1%±20% versus 14.9%±18.3%; P<0.01) after stenting. Renal vein biomarkers correlated with the degree of hypoxia in the STK: NGAL(r=0.3; P=0.01) and MCP-1(r=0.3; P=0.02; more so after stenting). Renal vein NGAL was inversely related to renal blood flow in the STK (r=-0.65; P<0.001). Biomarkers were highly correlated between STK and CLK, NGAL (r=0.94; P<0.001), and MCP-1 (r=0.96; P<0.001).

CONCLUSIONS

These results showed changes over time in single-kidney GFR that were not evident in parameters of total GFR. Furthermore, they delineate the relationship of measurable tissue hypoxia within the STK and markers of inflammation in human ARAS. Renal vein NGAL and MCP-1 indicated persistent interactions between the ischemic kidney and both CLK and systemic levels of inflammatory cytokines.

Compensatory Structural and Functional Adaptation after Radical Nephrectomy for Renal Cell Carcinoma According to Preoperative Stage of Chronic Kidney Disease

PURPOSE

We investigated structural hypertrophy and functional hyperfiltration as compensatory adaptations after radical nephrectomy in patients with renal cell carcinoma according to the preoperative chronic kidney disease stage.

MATERIALS AND METHODS

We retrospectively identified 543 patients who underwent radical nephrectomy for renal cell carcinoma between 1997 and 2012. Patients were classified according to preoperative glomerular filtration rate as no chronic kidney disease--glomerular filtration rate 90 ml/minute/1.73 m(2) or greater (230, 42.4%), chronic kidney disease stage II--glomerular filtration rate 60 to less than 90 ml/minute/1.73 m(2) (227, 41.8%) and chronic kidney disease stage III--glomerular filtration rate 30 to less than 60 ml/minute/1.73 m(2) (86, 15.8%). Computerized tomography performed within 2 months before surgery and 1 year after surgery was used to assess functional renal volume for measuring the degree of hypertrophy of the remnant kidney, and the preoperative and postoperative glomerular filtration rate per unit volume of functional renal volume was used to calculate the degree of hyperfiltration.

RESULTS

Among all patients (mean age 56.0 years) mean preoperative glomerular filtration rate, functional renal volume and glomerular filtration rate/functional renal volume were 83.2 ml/minute/1.73 m(2), 340.6 cm(3) and 0.25 ml/minute/1.73 m(2)/cm(3), respectively. The percent reduction in glomerular filtration rate was statistically significant according to chronic kidney disease stage (no chronic kidney disease 31.2% vs stage II 26.5% vs stage III 12.8%, p <0.001). However, the degree of hypertrophic functional renal volume in the remnant kidney was not statistically significant (no chronic kidney disease 18.5% vs stage II 17.3% vs stage III 16.5%, p=0.250). The change in glomerular filtration rate/functional renal volume was statistically significant (no chronic kidney disease 18.5% vs stage II 20.1% vs stage III 45.9%, p <0.001). Factors that increased glomerular filtration rate/functional renal volume above the mean value were body mass index (p=0.012), diabetes mellitus (p=0.023), hypertension (p=0.015) and chronic kidney disease stage (p <0.001).

CONCLUSIONS

Patients with a lower preoperative glomerular filtration rate had a smaller reduction in postoperative renal function than those with a higher preoperative glomerular filtration rate due to greater degrees of functional hyperfiltration.