Kidney-Failure Risk Projection for the Living Kidney-Donor Candidate

Development and validation of risk prediction model for post-donation renal function in living kidney donors

This study aimed to create and validate a predictive model for renal function following live kidney donation, using pre-donation factors. Accurately predicting remaining renal function post live kidney donation is currently insufficient, necessitating an effective assessment tool. A multicenter retrospective study of 2318 live kidney donors from two independent centers (May 2007-December 2019) was conducted. The primary endpoint was the reduction in eGFR to below 60 mL/min/m2 6 months post-donation. The primary endpoint was achieved in 14.4% of the training cohort and 25.8% of the validation cohort. Sex, age, BMI, hypertension, preoperative eGFR, and remnant kidney proportion (RKP) measured by computerized tomography (CT) volumetry were found significant in the univariable analysis. These variables informed a scoring system based on multivariable analysis: sex (male: 1, female: 0), age at operation (< 30: 0, 30-39: 1, 40-59: 2, ≥ 60: 3), preoperative eGFR (≥ 100: 0, 90-99: 2, 80-89: 4, < 80: 5), and RKP (≥ 52%: 0, < 52%: 1). The total score ranged from 0 to 10. The model showed good discrimination for the primary endpoint in both cohorts. The prediction model provides a useful tool for estimating post-donation renal dysfunction risk, factoring in the side of the donated kidney. It offers potential enhancement to pre-donation evaluations.

Successful Kidney Transplantation Using Elderly Living Donor with Extremely Large Renal Cyst and Double Arteries

The authors describe a kidney transplant procedure using a living donor with a large cyst and double arteries. Due to the lack of regular transplant activity from a deceased donors, we decided to use the, so called, expanded criteria living donors, which means older age (more than 65 years), hypertension, some structural anomalies of the kidneys (cysts, multiple renal arteries), ABO incompatible kidney transplant, etc. The surgical procedure was the unroofing of a large cyst and wadding with perirenal fat. The 10 years survival rate is quite successful and we can recommend it.

Crosstalk between ALK3(BMPR1A) deficiency and autophagy signaling mitigates pathological bone loss in osteoporosis

Postmenopausal osteoporosis is recognized to be one of the major skeleton diseases strongly associated with impaired bone formation. Previous reports have indicated that the importance of bone morphogenetic protein (BMP) signaling of osteoblast lineage in bone development via classical Smad signaling, however, its critical role in osteoporosis is still not well understood. In the current study, we aim to investigate the pathological role of BMPR1A, a key receptor of BMPs, in osteoporosis and its underlying mechanism. We first found that knockdown of BMPR1A by using Col1a1-creER in osteoblasts mitigated early bone loss of osteoporosis in mice, yet along with late bone maturation defects by reducing mineral adherence rate and bone formation rate in vivo. At the cellular level, we then observed that BMPR1A deficiency promoted the proliferation of pre-osteoblasts under osteoporotic conditions but hindered their late-stage mineralization. We finally elucidated that BMPR1A deficiency compensatorily triggered mTOR-autophagy perturbation by a higher level in early osteoporotic pre-osteoblasts thus resulting in the enhancement of transient cell proliferation but impairment of final mineralization. Taken together, this study indicated the significance of BMPR1A-mTOR/autophagy axis, as a double-edged sword, in osteoporotic bone formation and provided new cues for therapeutic strategies in osteoporosis.

Prognostic Models in Nephrology: Where Do We Stand and Where Do We Go from Here? Mapping Out the Evidence in a Scoping Review

Prognostic models can strongly support individualized care provision and well-informed shared decision making. There has been an upsurge of prognostic research in the field of nephrology, but the uptake of prognostic models in clinical practice remains limited. Therefore, we map out the research field of prognostic models for kidney patients and provide directions on how to proceed from here. We performed a scoping review of studies developing, validating, or updating a prognostic model for patients with CKD. We searched all published models in PubMed and Embase and report predicted outcomes, methodological quality, and validation and/or updating efforts. We found 602 studies, of which 30.1% concerned CKD populations, 31.6% dialysis populations, and 38.4% kidney transplantation populations. The most frequently predicted outcomes were mortality ( n =129), kidney disease progression ( n =75), and kidney graft survival ( n =54). Most studies provided discrimination measures (80.4%), but much less showed calibration results (43.4%). Of the 415 development studies, 28.0% did not perform any validation and 57.6% performed only internal validation. Moreover, only 111 models (26.7%) were externally validated either in the development study itself or in an independent external validation study. Finally, in 45.8% of development studies no useable version of the model was reported. To conclude, many prognostic models have been developed for patients with CKD, mainly for outcomes related to kidney disease progression and patient/graft survival. To bridge the gap between prediction research and kidney patient care, patient-reported outcomes, methodological rigor, complete reporting of prognostic models, external validation, updating, and impact assessment urgently need more attention.

Are Differences in Living Kidney Donation Rates a Sex or a Gender Disparity?

Sex-disaggregated data reveal significant disparities in living kidney donation, with more female than male living kidney donors in most countries and proportions over 60% in some countries. We summarize the present state of knowledge with respect to the potential drivers of this disparity and argue that it is primarily driven by gender-related factors. First, we present the differences between sex and gender and then proceed to summarize the potential medical reasons that have been proposed to explain why males are less likely to be living kidney donors than females, such as the higher prevalence of kidney failure in males. We then present counterarguments as to why biological sex differences are not enough to explain lower living kidney donation among males, such as a higher prevalence of chronic kidney disease among females, which could affect donation rates. We argue that gender differences likely provide a better explanation as to why there are more women than men living kidney donors and explore the role of economic and social factors, as well as gender roles and expectations, in affecting living kidney donation among both men and women. We conclude with the need for a gender analysis to explain this complex psychosocial phenomenon in living kidney donation.

Association of Pre- and Post-Donation Renal Function with Midterm Estimated Glomerular Filtration Rate in Living Kidney Donors: A Retrospective Study

PURPOSE

The estimated glomerular filtration rate (eGFR) at 6 months after donation (eGFR_6m) is strongly associated with the risk of end-stage renal disease in living kidney donors. This study aimed to investigate the incidence of eGFR_6m <60 mL/min/1.73 m² (eGFR_6m <60) and identify the risk factors that can predict the occurrence of eGFR_6m <60 in living kidney donors.

MATERIALS AND METHODS

Living kidney donors who underwent nephrectomy at Severance Hospital between January 2009 and December 2019 were identified. We excluded 94 of 1233 donors whose creatinine values at 6 months after donation were missing. The risk factors for eGFR_6m <60 were assessed using multivariate regression analysis. The optimal cutoff points for candidate risk factors for predicting eGFR_6m <60 occurrence were determined using the Youden index.

RESULTS

The eGFR_6m <60 occurred in 17.3% of the participants. Older age (≥44 years), history of hypertension, lower preoperative eGFR (<101 mL/min/1.73 m²), and degree of increase in creatinine levels on postoperative day 2 compared to those before surgery (ΔCr2_pre) (≥0.39 mg/dL) increased the risk of eGFR_6m <60. The addition of ΔCr2_pre to preoperative eGFR yielded a higher predictive accuracy for predicting eGFR_6m <60 than that with preoperative eGFR alone {area under the receiver operating characteristic curve=0.886 [95% confidence interval (CI), 0.863-0.908] vs. 0.862 (95% CI, 0.838-0.887), p<0.001}.

CONCLUSION

The incidence of eGFR_6m <60 was 17.3%. Older age, lower preoperative eGFR, history of hypertension, and greater ΔCr2_pre were associated with the occurrence of eGFR_6m <60 after living donor nephrectomy. The combination of preoperative eGFR and ΔCr2_pre showed the highest predictive power for eGFR_6m <60.

Pregnancy outcomes after living kidney donation from a nationwide population-based cohort study from Korea

While most living kidney donors experience good outcomes and high rates of satisfaction, kidney donation can increase the risk of gestational hypertension or preeclampsia. However, pregnancy outcomes in non-white donors are limited. We conducted a nationwide cohort study of 112 living kidney donors and 672 matched healthy non-donors using the Korean National Health Insurance Claims Database. Donors and healthy non-donors were matched according to age, year of cohort entry, residency, income, number of pregnancies, and the time to the first pregnancy after cohort entry. We assessed pregnancy outcomes of live kidney donors compared with matched healthy non-donors using the nationwide database. Gestational hypertension or preeclampsia was more common in kidney donors than in non-donors (8.9% vs. 1.8%; adjusted odds ratio, 2.68; 95% confidence interval, 1.11-6.50). However, the incidence of severe gestational hypertension or preeclampsia that required antihypertensive medication was comparable (2.7% vs. 0.9%; P = 0.121). The time from donation to delivery within 5 years and primiparity were risk factors for preeclampsia in donors. Low birth weight, stillbirth, and ectopic pregnancy were not significantly different between the two groups. Maternal death occurred in two non-donor cases, but none occurred in donors compared to non-donors. Our findings indicate that kidney donors are associated with an increased risk of gestational hypertension or preeclampsia than matched healthy non-donors. However, the probabilities of serious maternal and fetal outcomes remained low and are not increased significantly after kidney donation.

Assessing Renal Function for Kidney Donation. How Low Is Too Low?

Kidney transplantation (KT) is the treatment of choice for patients with end-stage kidney disease (ESKD) with decreased morbi-mortality, improved life quality, and reduced cost. However, the shortage of organs from deceased donors led to an increase in KT from living donors. Some stipulate that living donors have a higher risk of ESKD after donation compared with healthy non-donors. The reason for this is not clear. It is possible that ESKD is due to the nephrectomy-related reduction in glomerular filtration rate (GFR), followed by an age-related decline that may be more rapid in related donors. It is essential to assess donors properly to avoid rejecting suitable ones and not accepting those with a higher risk of ESKD. GFR is a central aspect of the evaluation of potential donors since there is an association between low GFR and ESKD. The methods for assessing GFR are in continuous debate, and the kidney function thresholds for accepting a donor may vary according to the guidelines. While direct measurements of GFR (mGFR) provide the most accurate evaluation of kidney function, guidelines do not systematically use this measurement as a reference. Also, some studies have shown that the GFR decreases with age and may vary with gender and race, therefore, the lower limit of GFR in patients eligible to donate may vary based on these demographic factors. Finally, it is known that CrCl overestimates mGFR while eGFR underestimates it, therefore, another way to have a reliable GFR could be the combination of two measurement methods.

The spectrum of kidney function alterations in adolescents with a solitary functioning kidney

BACKGROUND

A precise assessment of glomerular filtration rate is key to delineate the care of children with a solitary functioning kidney (SFK). Data regarding measured GFR (mGFR) in this population is restricted to a single study of 77 individuals, which suggested that a GFR estimation (eGFR) method based on creatinine and cystatin C (eGFR-CKiD2) performed better than Schwartz's equation (eGFR-Schwartz).

METHODS

We measured GFR in 210 consecutive adolescents (7 to 22 years old) with an SFK referred to our institution between 2014 and 2019 and in 43 young candidates for kidney donation (18 to 25 years old). We compared the distribution of mGFR in both groups and determined the factors associated with reduced mGFR in adolescents with an SFK. We further compared different eGFR formulas with mGFR and assessed the association of mGFR and eGFRs with PTH and FGF23, two early indicators of GFR reduction.

RESULTS

While adolescents with an SFK had a similar median mGFR to healthy controls (103 ± 24ml/min/1.73m² vs. 107 ± 12 ml/min/1.73m²), the fraction of individuals with an mGFR below 90 ml/min/1.73m² was higher in patients with SFK (23% vs. 5% in controls; P = 0.005). Multiple linear regression identified older age, ipsilateral abnormalities of the urinary tract, lack of compensatory hypertrophy, and treated hypertension as independent factors associated with reduced mGFR. A smaller bias using eGFR-Schwartz (95% confidence interval (95%CI): 3 to 7) was revealed when compared to other eGFR. Compared to eGFR-Schwartz, mGFR showed a stronger correlation with PTH (r = 0.04 vs. r = 0.1) and FGF23 (r = 0.03 vs. r = 0.05).

CONCLUSION

SFK is not a benign condition, since 20% of the patients display altered kidney function. Our results raise caution regarding the use of the cystatin-based equation. mGFR shows a better ability than eGFR-Schwartz to differentiate patients showing early homeostatic adaptation to GFR reduction.

Outcomes of Hypertensive Kidney Donors Using Current and Past Hypertension Definitions

Introduction

As many as 50% of U.S. transplant centers do not accept kidney donor candidates with hypertension, citing the link between hypertension, kidney disease, and cardiovascular disease (CVD).

Methods

We ascertained mortality, CVD, proteinuria, estimated glomerular filtration rate (eGFR) trajectory, reduced eGFR, and end-stage kidney disease (ESKD) in 904 hypertensive donors (blood pressure [BP] ≥140/90 mm Hg or receiving treatment) versus 7817 donors with BP <140/90 mm Hg.

Results

Hypertensive donors were older, 58.1% were <50 years of age, and they had a lower eGFR. The majority were white and related to their recipient. At the end of follow-up, 14.3 ± 10.1 years (range 4-48 years) from donation, hypertensive and nonhypertensive donors had a similar prevalence of cardiovascular disease and renal outcomes. The multivariable risk of mortality, CVD, and proteinuria were also comparable in normotensive and hypertensive donors. eGFR slope over time was similar in hypertensive and nonhypertensive donors, and in total 5 hypertensive and 39 normotensive donors developed ESKD 19.2 ± 10.3 years after donation (adjusted hazard ratio 1.14 [95% confidence interval 0.62-2.12], P = 0.67). Sensitivity analysis using the new definition of hypertension (≥130/80 mm Hg or requiring treatment) yielded similar results for renal outcomes, but hypertensive donors were more likely to develop CVD and diabetes.

Conclusions

Kidney donors with hypertension defined by past criteria do not appear to incur higher mortality, CVD, or ESKD. Donors with current definition of hypertension enjoyed similar renal outcomes but were more likely to develop CVD.

The present and future of transplant organ shortage: some potential remedies

Transplantation remains the modality of choice for patients with end stage renal disease (ESRD). However, while there has been a steady rise in the number of patients with ESRD the supply of donors (combine living and deceased) has fallen far behind the need, resulting in an increasing number of qualified patients remaining on the wait-list, and thousands being removed from the list every year because of death or becoming too sick for transplantation. This has also fed to transplant tourism around the world. Several countries have implemented a variety of policies to overcome their organ shortage that are presented in this article. There is an urgent need for developing policies geared to the cultural norms of different societies and universally accepted ethical principles to remedy this public health issue.

Living kidney donation in individuals with hepatitis C and HIV infection: rationale and emerging evidence

PURPOSE OF REVIEW

HIV-infected (HIV+) and hepatitis C virus-infected (HCV+) individuals with end-stage renal disease (ESRD) have decreased access to kidney transplantation. With new opportunities provided by the HIV Organ Policy Equity (HOPE) Act and direct-acting antivirals (DAAs) for HCV, we explore the potential risks and benefits of living donor kidney transplantation from HIV+ or HCV+ donors, from the perspective of both donor health and recipient outcomes.

RECENT FINDINGS

The HOPE Act permits organ donation from both deceased and living HIV+ persons to HIV+ recipients; however, there is only clinical experience with HIV+ deceased donors to date. Empirical evidence demonstrates a low but acceptable risk of ESRD in potential HIV+ living donors without comorbidities who have well-controlled infection in the absence of donation. With the availability of potent DAAs for eradication of HCV infection, growing evidence shows good outcomes with HCV seropositive and/or viremic deceased kidney donors, providing rationale to consider HCV+ living donors.

SUMMARY

HIV+ and HCV+ living donor kidney transplantation may improve access to transplant for vulnerable ESRD populations. Careful evaluation and monitoring are warranted to mitigate potential risks to donors and recipients.

Hyperfiltration-mediated Injury in the Remaining Kidney of a Transplant Donor

Kidney donors face a small but definite risk of end-stage renal disease 15 to 30 years postdonation. The development of proteinuria, hypertension with gradual decrease in kidney function in the donor after surgical resection of 1 kidney, has been attributed to hyperfiltration. Genetic variations, physiological adaptations, and comorbidities exacerbate the hyperfiltration-induced loss of kidney function in the years after donation. A focus on glomerular hemodynamics and capillary pressure has led to the development of drugs that target the renin-angiotensin-aldosterone system (RAAS), but these agents yield mixed results in transplant recipients and donors. Recent work on glomerular biomechanical forces highlights the differential effects of tensile stress and fluid flow shear stress (FFSS) from hyperfiltration. Capillary wall stretch due to glomerular capillary pressure increases tensile stress on podocyte foot processes that cover the capillary. In parallel, increased flow of the ultrafiltrate due to single-nephron glomerular filtration rate elevates FFSS on the podocyte cell body. Although tensile stress invokes the RAAS, FFSS predominantly activates the cyclooxygenase 2-prostaglandin E2-EP2 receptor axis. Distinguishing these 2 mechanisms is critical, as current therapeutic approaches focus on the RAAS system. A better understanding of the biomechanical forces can lead to novel therapeutic agents to target FFSS through the cyclooxygenase 2-prostaglandin E2-EP2 receptor axis in hyperfiltration-mediated injury. We present an overview of several aspects of the risk to transplant donors and discuss the relevance of FFSS in podocyte injury, loss of glomerular barrier function leading to albuminuria and gradual loss of renal function, and potential therapeutic strategies to mitigate hyperfiltration-mediated injury to the remaining kidney.

Mortality in Living Kidney Donors With ESRD: A Propensity Score Analysis Using the United States Renal Data System

Introduction

In recent years, data have emerged on the outcomes of living kidney donors who develop end-stage renal disease (ESRD). We aimed to evaluate mortality rates in kidney donors who had initiated dialysis compared with a propensity-matched cohort of dialysis patients without previous kidney donation.

Methods

We used the United States Renal Data System (USRDS) and abstracted 274 previous living kidney donors between 1995 and 2009. There were 609,398 individuals on dialysis without kidney donation. We used propensity score matching to identify 258 donors and 258 nondonors. The time-dependent Cox proportional hazards model was used to compare survival between the 2 matched cohorts.

Results

In the propensity score−matched cohort, mortality was lower in donors compared with nondonors (19% vs. 49%; P < 0.0001). The time-dependent Cox proportional hazards model demonstrated that donors had significantly lower mortality compared with nondonors 0 to 5 years since start of dialysis (hazard ratio [HR]: 0.17; 95% confidence interval [CI] 0.11−0.27; P < 0.0001) and with nondonors 5 to 10 years on dialysis (HR: 0.34; 95% CI: 0.19−0.63; P < 0.001). We were unable to estimate the difference between the 2 groups after 10 years on dialysis with any precision (HR: 0.51; 95% CI: 0.18−1.42; P = 0.20) due to the small sample size.

Conclusion

We observed a lower mortality rate in living kidney donors with ESRD compared with matched nondonors. This data should guide clinicians in the informed consent process with prospective donors.

Long-term risks of kidney living donation: review and position paper by the ERA-EDTA DESCARTES working group

Two recent matched cohort studies from the USA and Norway published in 2014 have raised some concerns related to the long-term safety of kidney living donation. Further studies on the long-term risks of living donation have since been published. In this position paper, Developing Education Science and Care for Renal Transplantation in European States (DESCARTES) board members critically review the literature in an effort to summarize the current knowledge concerning long-term risks of kidney living donation to help physicians for decision-making purposes and for providing information to the prospective live donors. Long-term risk of end-stage renal disease (ESRD) can be partially foreseen by trying to identify donors at risk of developing ‘de novo’ kidney diseases during life post-donation and by predicting lifetime ESRD risk. However, lifetime risk may be difficult to assess in young donors, especially in those having first-degree relatives with ESRD. The study from Norway also found an increased risk of death after living donor nephrectomy, which became visible only after >15 years of post-donation follow-up. However, these findings are likely to be largely the result of an overestimation due to the confounding effect related to a family history of renal disease. DESCARTES board members emphasize the importance of optimal risk–benefit assessment and proper information to the prospective donor, which should also include recommendations on health-promoting behaviour post-donation.

Summary of Kidney Disease: Improving Global Outcomes (KDIGO) Clinical Practice Guideline on the Evaluation and Care of Living Kidney Donors

Kidney Disease: Improving Global Outcomes (KDIGO) engaged an evidence review team and convened a work group to produce a guideline to evaluate and manage candidates for living kidney donation. The evidence for most guideline recommendations is sparse and many "ungraded" expert consensus recommendations were made to guide the donor candidate evaluation and care before, during, and after donation. The guideline advocates for replacing decisions based on assessments of single risk factors in isolation with a comprehensive approach to risk assessment using the best available evidence. The approach to simultaneous consideration of each candidate's profile of demographic and health characteristics advances a new framework for assessing donor candidate risk and for defensible shared decision making.

Understanding and Communicating Medical Risks for Living Kidney Donors: A Matter of Perspective

Communicating the current knowledge of medical outcomes after live kidney donation necessary to support donor candidates in well informed decision-making requires grounding in perspectives of comparison. Baseline risk (without donating), risk attributable to donation, and absolute risk (after donating) need to be considered. Severe perioperative complications and death are rare, but vary by demographic, clinical, and procedure factors. Innovative capture of "healthy" controls designed to simulate donor selection processes has identified higher risk of ESRD attributable to donation in two studies; importantly, however, the absolute 15-year ESRD incidence in donors remains very low (0.3%). In the first decade after donation, the risk of all-cause mortality and cardiovascular events is no higher than in healthy nondonors. Pregnancies in donors may incur attributable risk of gestational hypertension or preeclampsia (11% versus 5% incidence in one study). A modest rise in uric acid levels beginning early after donation, and a small (1.4%) increase in the 8-year incidence of gout, have also been reported in comparisons to healthy nondonors. As in the general population, postdonation outcomes vary by race, sex, and age. Efforts to improve the counseling and selection of living donors should focus on developing tools for tailored risk prediction according to donor characteristics, and ideally, compared with similar healthy nondonors.