Living Donor Kidney Volume as a Predictor of Graft Function: Is There a Role for Proteinuria?

Acute kidney injury and the compensation of kidney function after nephrectomy in living donation

Acute kidney injury (AKI) incidence is growing rapidly, and AKI is one of the predictors of inpatient mortality. After nephrectomy, all the patients have decreased kidney function with AKI and recover from AKI. However, the characteristic and behavior of AKI is different from usual AKI and compensatory kidney function has been well known in the postoperative setting, especially in living donors. In this review, we have focused on the compensation of kidney function after nephrectomy in living donors. We discuss factors that have been identified as being associated with kidney recovery in donors including age, sex, body mass index, remnant kidney volume, estimated glomerular filtration rate, and various comorbidities.

Is Compensation Prediction Score Valid for Contralateral Kidney After Living-Donor Nephrectomy in the United States?

BACKGROUND

Compensation after living donor nephrectomy is well known, and a compensation prediction score (CPS) was made in Japan previously. The aim of this study was to perform external validation of CPS in the United States.

METHODS

We studied retrospectively 78 living donor nephrectomies in our institution. We defined a favorable compensation as a postdonation estimated glomerular filtration rate (eGFR) at 1 year of >60% of the predonation eGFR. We analyzed the living donors' clinical characteristics and outcomes and validated CPS score.

RESULTS

The median (range) donor age was 43 (21-63) years, and median body mass index was 26.9 (18.3-35.9) kg/m². Forty-four percent of donors were White. The donor predonation eGFR was 105 (61-134) mL/min/1.73 m², and the postdonation eGFR at 1 year was 73.2 (0-115) mL/min/1.73 m². Eighty-three percent of donors had a favorable compensation. The CPS was 9.6 (1.6-15.6) and showed strong diagnostic accuracy for predicting favorable compensation (area under the curve, 0.788; 95% confidence interval, 0.652-0.924; P = .001). The CPS showed a significant positive correlation with the postdonation eGFR at 1 year (R = 0.54; P < .001).

CONCLUSIONS

In the United States, the CPS would be a valid tool with which to predict a favorable compensation of remnant kidney function.

Long Hemodialysis Duration Predicts Delayed Graft Function in Renal Transplant Recipients From Living Donor: A Single-Center Study

BACKGROUND

This study aims to determine the ratio of delayed graft function in renal transplant recipients from living donors and the predictive value of hemodialysis time before transplant for delayed graft function.

METHODS

We conducted a study on 116 adult patients who were diagnosed with end-stage kidney disease and were treated with hemodialysis and transplanted kidneys from living donors for 2 years (from June 2018 to June 2020). Delayed graft function event was collected for each patient.

RESULTS

The recipients had a median age of 36.5 years old, in which 55.2% of them were men, 4.3% of them had the diabetic mellitus, and the median hemodialysis duration was 6 months. The ratio of positive panel-reactive antibody was 33.6% and vascular reconstruction of the donor's kidney was 16.4%. The ratio of delayed graft function was 12.2% (14 of 116 patients). Delayed graft function significantly related to positive panel-reactive antibody, long duration of hemodialysis before transplant, and vascular reconstruction of donor's kidney with P < .001. Duration of hemodialysis before kidney transplant had a predictive value for delayed graft function (area under the curve, 0.83; P < .001).

CONCLUSION

Delayed graft function was not rare in renal transplant recipients from living donors. Duration of hemodialysis before kidney transplant was a good predictor for delayed graft function.

A SNP in the 3'UTR of the porcine IGF-1 gene interacts with miR-new14 to affect IGF-1 expression, proliferation and apoptosis of PK-15 cells

The kidney of miniature pigs has been considered the most likely potential kidney source for patients needing kidney transplantation. Insulin-like growth factor 1 (IGF-1) is involved in regulating the growth of miniature pigs and inducing growth of kidneys. There are evidences showing that the SNPs in the 3'UTR of a gene may affect the gene expression by affecting the binding to a miRNA target site. In this study, one SNP (rs34142920) was screened in the IGF-1 3'UTR between 2 different body types of porcine breeds, Bama Xiang (BX) pigs, a miniature pig breed, and Large White (LW) pigs by sequencing. The secondary structure of the IGF-1 3'UTR mRNA containing the SNP in BX pigs is different from that of LW pigs. We then verified that there was a porcine miRNA (miR-new14) binding to this SNP in the 3'UTR of IGF-1 via cotransfecting the 3'UTR from the 2 breeds and miR-new14. We further found that the SNP downregulated mRNA and protein levels of IGF-1 by affecting the binding of miR-new14. To understand the function of miR-new14 in porcine kidney (PK-15) cells and its mechanism, cell proliferation and cell apoptosis assays were employed and results showed that proliferation viability of PK-15 cells was weakened and the apoptotic percentage of PK-15 cells was higher in the miR-new14 group. Porcine miRNA reduced the mRNA expression of AKT/ERK and protein levels of p-AKT/p-ERK. These results suggested that the expression of IGF-1 is influenced by this SNP and miR-new14 and that miR-new14 may suppress cell proliferation and promote cell apoptosis in PK-15 cells through regulating AKT and ERK signaling pathways, in which IGF-1 is involved.

Prediction model of compensation for contralateral kidney after living-donor donation

Background

Compensation of contralateral kidney function after living-donor kidney donation is well known, and many predictive factors have been proposed. However, no prediction model has been proposed. This study was performed to establish a tool with which to estimate the degree of compensation of the contralateral kidney after living-donor kidney donation.

Methods

We retrospectively analyzed 133 living donors for renal transplantation in our institution. We defined a favorable compensation as a post-donation estimated glomerular filtration rate (eGFR) at 1 year (calculated by the Chronic Kidney Disease Epidemiology Collaboration equation) of > 60% of the pre-donation eGFR. We analyzed the living donors’ clinical characteristics and outcomes.

Results

The median (range) donor age was 59 (24–79) years, median (range) body mass index was 22.9 (16.8–32.7) kg/m², and median (range) body surface area was 1.6 (1.3–2.0) m². All donors were Japanese, and 73% of the donors were biologically related. The median (range) donor pre-donation eGFR was 108.7 (82–144) ml/min/1.73 m², and the median (range) post-donation eGFR at 1 year was 86.9 (43–143) ml/min/1.73 m². Eighty-six percent of donors had compensatory hypertrophy. In the univariate analysis, age, female sex, history of hypertension, body surface area, and pre-donation eGFR were significantly associated with hypertrophy (p < 0.05). In the multivariate analysis, age, female sex, history of hypertension, and ratio of the remnant kidney volume to body weight were significantly associated with hypertrophy (p < 0.05). Based on these results, we created a compensation prediction score (CPS). The median (range) CPS was 8.7 (1.1–17.4). Receiver operating characteristic analysis showed strong diagnostic accuracy for predicting favorable compensation (area under the curve, 0.958; 95% confidence interval, 0.925–0.991, p < 0.001). The optimal cut-off value of the CPS was 5.0 (sensitivity, 92.0%; specificity, 89.5%). The CPS had a strong positive correlation with the post-donation eGFR (R = 0.797, p < 0.001).

Conclusion

The CPS might be useful tool with which to predict a favorable compensation of the contralateral kidney and remnant kidney function. If the CPS is low, careful management and follow-up might be necessary. Further investigations are needed to validate these findings in larger populations.

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.

Impact of remaining kidney volume to body weight ratio on renal function in living kidney donors

To investigate whether the ratio of remnant kidney volume to body weight (V/W ratio) can impact renal function in donors, 45 living kidney donors were enrolled. Kidney volume was analyzed by magnetic resonance imaging. Renal function was compared between donors with a V/W ratio of < 2.0 mL/kg (n = 23) or ≥ 2.0 mL/kg (n = 22). Donors in both V/W groups showed similar serum creatinine levels and estimated glomerular filtration rates (eGFRs) at 7 days and 1 year, whereas donors with a V/W ratio of < 2.0 mL/kg had significantly higher 24-hour urine protein levels at 1 year (0.54 ± 0.23 g/d vs. 0.33 ± 0.19 g/d, p = 0.028). Multivariate analysis revealed no correlation between the V/W ratio and eGFR at 7 days or 1 year, and a V/W ratio of < 2 mL/kg was not associated with an increased incidence of eGFR < 60 mL/min/1.73 m(2) at 1 year (risk ratio 1.73, 95% confidence interval 0.10-29.47). The V/W ratio correlated inversely with 24-hour urine protein (r = -0.377, p = 0.021) at 1 year, and donors with a V/W ratio of < 2.0 mL/kg were more likely to show 24-hour urine protein >300 mg (risk ratio 1.70, 95% confidence interval 1.08-2.67) at 1 year. Donors with lower V/W ratios have higher 24-hour urinary protein levels at 1 year after transplantation. These findings suggest that the V/W ratio may be useful for kidney selection.

Does allograft size really matter in the long-term outcome of living donor kidney transplantation?

BACKGROUND

Increased allograft mass in living donor kidney transplantation has been recognized as a predictor factor of better short-term allograft function. We evaluated whether donor kidney volume adjusted for recipient body weight is associated with long-term allograft function in living donor kidney transplantation.

METHODS

We analyzed 67 living donors and their recipients who underwent transplantation between 2003 and 2007. Estimated glomerular filtration rate (eGFR) and serum creatinine levels at 1, 2, 3, 4, and 5 years post-transplantation were recorded for all recipients. Transplanted kidney volumes were measured using 3-D helical computed tomography scanning. A transplant kidney volume-recipient body weight (Vol/Wt) ratio was calculated for each donor-recipient pair. The subjects were divided into tertiles according to Vol/Wt ratios: low (<2.16), medium (2.16-2.88), and high (>2.88).

RESULTS

Vol/Wt ratio significantly correlated with recipient eGFR and serum creatinine levels at 1, 2, 3, and 4 years post-transplantation (r = .48, P < .0001; r = .46, P < .0001; r = .47, P < .0001; r = .26, P = .037, respectively, for eGFR; r = -.53, P < .0001; r = -.50, P < .0001; r = -.44, P < .0001; r = -.37, P = .003, respectively, for serum creatinine) but not at 5 years (r = .12, P = .406 for eGFR; r = -.21, P = .110 for serum creatinine). Whereas recipient eGFR increased significantly in a graded fashion among low to high Vol/Wt ratio groups during 1 to 3 years post-transplantation, there was no difference in eGFR values between Vol/Wt ratio groups at 4 and 5 years (P = .21 and .71, respectively).

CONCLUSION

Vol/Wt ratio is not associated with long-term allograft function in living donor kidney transplantation.

Simplified method to measure renal volume: the best correction factor for the ellipsoid formula volume calculation in pretransplant computed tomographic live donor

OBJECTIVE

To find an optimal correction factor that will produce a near-real renal volume calculation using the ellipsoid formula.

METHODS

We retrospectively studied 79 multidetector computed tomography (MDCT) examinations for potential renal donor assessment. The renal volumes were calculated using the slice summation method, the ellipsoid formula with π/6 as correction factors as well multiple other correction factors for statistical analysis. A paired Student t test was used for evaluating the volumes calculated with different correction factors and the volumes calculated by the slice summation method.

RESULTS

The ellipsoid formula using correction factor 0.524 underestimates the renal volume by approximately 22.2% with statistical difference compared with the slice summation method (P<.05). There is no statistical difference when using correction factor in the range of 0.664 to 0.686 (P>.05). Further subgroup analysis of gender and laterality was performed and revealed no statistical difference. Using a mean value of 0.674 or 0.67 as correction factor results in renal volumes that are 100% and 99.5%.

CONCLUSION

To avoid underestimation of the renal volume by the ellipsoid method, acceptable correction factors are in the range of 0.664 to 0.686. We suggest the use of a mean value of 0.674 or 0.67 as correction factor when using the ellipsoid formula.