CT volumetry is superior to nuclear renography for prediction of residual kidney function in living donors

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.

Assessing asymmetrical kidney function in living donors: a retrospective cohort study on CT metrics

BACKGROUND

Live donor kidney transplantation is the preferred kidney replacement therapy for eligible patients but requires thorough donor evaluation to minimise risks. Contemporary guidelines recommend split kidney function measurement in living donors only when there is a significant kidney size discrepancy, yet the evidence for this is poor, and practice varies nationally. This study evaluates the efficacy of CT-derived kidney metrics in detecting significant functional asymmetry.

METHODS

We conducted a retrospective cohort analysis of 123 prospective living kidney donors at a regional transplant centre from June 2011 to October 2014, utilising CT to determine kidney and cortical volumes and lengths. Asymmetric kidney function (AKF), defined by > 10% function difference on DMSA scans, was correlated with CT measurements to calculate the diagnostic accuracy of current guidelines.

RESULTS

Among the prospective donors, the median age was 42 years, and 59.3% were female. The median split kidney function difference was 4%, with 25 individuals exhibiting > 10% AKF. Kidney length discrepancy proved to be a poor indicator of AKF (sensitivity: 28%, specificity: 84%). While negative predictive values for cortical and kidney volumes were high (96% and 93%, respectively), sensitivity was low, and specificity and positive predictive value did not meet satisfactory thresholds.

CONCLUSIONS

CT-derived metrics of kidney length, cortical, and total volume show limited sensitivity and specificity in identifying significant AKF. These findings provide evidence to support revised guideline development in the assessment of living kidney donors.

Can CT or MRI volumetry substitute scintigraphy in living kidney donor evaluation? A systematic review

BACKGROUND

Current potential living kidney donor's assessment includes functional and anatomical evaluation. Scintigraphy is recommended in some cases and some centers include this test in the donor's protocol. Recent studies advocate for the avoidance of this test as CT or MRI volumetry showed to accurately assess donor's renal function.

OBJECTIVE

To summarize scientific evidence on image tests for pre-donation and/or post-nephrectomy renal function evaluation.

EVIDENCE ACQUISITION

This review followed the guidelines set by the European Association of Urology and adhered to PRISMA 2020 recommendations. The protocol was registered in PROSPERO on 10th December 2022 (ID: CRD42022379273).

EVIDENCE SYNTHESIS

Twenty-one studies met the inclusion criteria after thorough screening and eligibility assessment. According to QUADAS-2, patient selection and flow/timing domains showed a predominant low risk of bias. The correlation between split renal function (SRF) using CT and scintigraphy varied from weak (r = 0.21) to remarkably strong (r = 0.949). Bland-Altman agreement demonstrated moderate to excellent results, with mean differences ranging from -0.06% to 1.76%. The correlation between split renal volume (CT) and estimated glomerular filtration rate (eGFR) at 6 months or 1 year after nephrectomy showed a moderate correlation, with coefficients ranging from 0.708 to 0.83. The correlation between SRF (MRI) and renal scintigraphy reported a moderate correlation, with correlation coefficients of 0.58 and 0.84. MRI and scintigraphy displayed a good agreement, with a 66% agreement observed and mean differences of ± 0.3%.

CONCLUSIONS

Despite study heterogeneity, MRI or CT-based renal volumetry appears promising compared to scintigraphy, with favorable correlations and agreement.

Choosing the larger kidney on CT volumetry: a study on the early post-donation kidney function of living donors

BACKGROUND

Selecting the smaller kidney for donation has been advocated if there is a size difference of > 10% between the 2 kidneys but has never been prospectively evaluated. With increase in donor nephrectomies, it is important to evaluate this to minimize loss of renal function to donors.

METHODS

75 consecutive donor nephrectomy patients were included in our longitudinal study. The Split Renal Volume (SRV) of bilateral kidneys were measured using contrasted computer tomography scans and patients segregated into 2 groups depending on donated kidney having more (Group 1) or less than (Group 2) 52.5% of SRV.

RESULTS

Patients in Group 1 (n = 19) and 2 (n = 56) were of similar age (43.8 vs. 48.3), BMI (22.4 vs. 25.2), sex (57.9 vs. 55.4% women), respectively. Although total kidney volumes were similar in both groups, Group 1 had significantly smaller right kidney volumes (120.4 ± 24.9 vs. 142.7 ± 28.4 mls, p = 0.003). EGFR pre-operatively (116.3 ± 20.8 vs. 106.3 ± 23.8 mL/min/1.73 m2) and at 6-months (65.7 ± 13.3 vs. 66.9 ± 15.5 mL/min/1.73 m2) were not different between groups. However, patients in Group 1 had significantly greater absolute (50.6 ± 14.9 vs. 39.5 ± 14.7 mL/min/1.73 m2) and relative decline (43.0 ± 8.6 vs. 36.3 ± 10.6%) in eGFR at 6 months (p = 0.06, 0.009).

CONCLUSION

With a SRV difference of 5% between the 2 sides, removal of the larger kidney for living kidney donation resulted in greater early decline of renal function than kidney donors whose larger or equivalent kidney is preserved.

CT volumetry performs better than nuclear renography in predicting estimated renal function one year after living donation

The evaluation of split renal function (SRF) is a critical issue in living kidney donations and can be evaluated using nuclear renography (NR) or computerized tomography (CT), with unclear comparative advantages. We conducted this retrospective study in 193 donors to examine the correlation of SRF assessed by NR and CT volumetry and compared their ability to predict remaining donor renal function at 1 year, through multiple approaches. A weak correlation between imaging techniques for evaluating the percentage of the remaining kidney volume was found in the global cohort, with an R² = 0.15. However, the Bland-Altman plot showed an acceptable agreement (95% of the difference between techniques falling within - 8.51 to 6.11%). The predicted and observed eGFR one year after donation were calculated using the CKD-EPI, and CG/BSA equations. CT volume showed a better correlation than NR for both formulas (adjusted R² of 0.42. and 0.61 vs 0.37 and 0.61 for CKD-EPI and CG/ BSA equations, respectively). In non-nested modeling tests, CT volumetry was significantly superior to NR for both equations. CT volumetry performed better than NR in predicting the estimated renal function of living donors at 1-year, independently from the eGFR equation.

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.

CT-measured Cortical Volume Ratio Is an Accurate Alternative to Nuclear Medicine Split Scan Ratio Among Living Kidney Donors

BACKGROUND

The 125I-iothalamate clearance and 99mTc diethylenetriamine-pentaacetic acid (99mTc-DTPA) split scan nuclear medicine studies are used among living kidney donor candidates to determine measured glomerular filtration rate (mGFR) and split scan ratio (SSR). The computerized tomography-derived cortical volume ratio (CVR) is a novel measurement of split kidney function and can be combined with predonation estimated GFR (eGFR) or mGFR to predict postdonation kidney function. Whether predonation SSR predicts postdonation kidney function better than predonation CVR and whether predonation mGFR provides additional information beyond predonation eGFR are unknown.

METHODS

We performed a single-center retrospective analysis of 204 patients who underwent kidney donation between June 2015 and March 2019. The primary outcome was 1-y postdonation eGFR. Model bases were created from a measure of predonation kidney function (mGFR or eGFR) multiplied by the proportion that each nondonated kidney contributed to predonation kidney function (SSR or CVR). Multivariable elastic net regression with 1000 repetitions was used to determine the mean and 95% confidence interval of R2, root mean square error (RMSE), and proportion overprediction ≥15 mL/min/1.73 m2 between models.

RESULTS

In validation cohorts, eGFR-CVR models performed best (R2, 0.547; RMSE, 9.2 mL/min/1.73 m2, proportion overprediction 3.1%), whereas mGFR-SSR models performed worst (R2, 0.360; RMSE, 10.9 mL/min/1.73 m2, proportion overprediction 7.2%) (P < 0.001 for all comparisons).

CONCLUSIONS

These findings suggest that predonation CVR may serve as an acceptable alternative to SSR during donor evaluation and furthermore, that a model based on CVR and predonation eGFR may be superior to other methods.

Remnant renal volume can predict prognosis of remnant renal function in kidney transplantation donors: a prospective observational study

Background

Safety and survival during and after donor nephrectomy (DN) are one of the main concerns in living kidney donors (LKDs). Therefore, kidney (left/right) to be procured should be determined after considering the difficulty of DN, as well as the preservation of remnant renal function (RRF). In this prospective study, we investigated the roles of computed tomography volumetry (CTV) in split renal function (SRF) and established a predictive model for RRF in LKDs.

Methods

We assessed 103 LKDs who underwent DN at our institute. The Volume Analyzer SYNAPSE VINCENT image analysis system were used as CTV. RRF was defined as the estimated glomerular filtration rate (eGFR) 12 months after DN. The association between various factors measured by CTV and RRF were investigated, and a role of CTV on prediction for RRF was assessed.

Results

The median age and the preoperative eGFR were 58 years and 80.7 mL/min/1.73m², respectively. Each factor measured by CTV showed an association with RRF. The ratio of remnant renal volume to body surface area (RRV/BSA) could predict RRF. In addition, RRV/BSA could predict RRF more accurately when used together with age and 24-h creatinine clearance (CrCl).

Conclusions

Our findings suggest that RRV/BSA measured by CTV can play an important role in predicting RRF, and a comprehensive assessment including age and CrCl is important to determine the kidney to be procured.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-021-02568-8.

Clinical Impact of Subclinical Interstitial Fibrosis or Tubular Atrophy in 1-Hour Allograft Biopsy for Remnant Renal Function in Living Kidney Donors: A Prospective Observational Study

BACKGROUND

Preservation of remnant renal function (RRF) is one of the major concerns among living kidney donors (LKDs). A comprehensive assessment is needed to predict the RRF. In this prospective study, we investigated the roles of histologic findings from a 1-hour allograft biopsy in predicting the RRF.

METHODS

Our prospective study included 116 LKDs who underwent donor nephrectomy (DN) at our institute. Clinical and radiographic data were obtained from their medical charts. Renal volume parameters were calculated using the preoperative computed tomographic images in the volume analyzer SYNAPSE VINCENT image analysis system. Tissues obtained from allograft biopsy were examined. RRF was defined as the estimated glomerular filtration rate (eGFR) 12 months after DN.

RESULTS

Of 116 LKDs, 95 were finally evaluated. The median age of the LKDs at DN and the preoperative eGFR were 57 years and 80.0 mL/min/1.73 m², respectively. In the histologic analysis, 68 allografts (71.6%) had nonspecific findings involving the glomerulus, vessel, and tubulointerstitium. Interstitial fibrosis or tubular atrophy (IF/TA) was the only significant predictive factor for RRF (P = .039). No significant association was found between renal volume parameters and IF/TA, whereas remnant renal volume adjusted by body weight (RRV/BW) tended to be relatively correlated with IF/TA (P = .072). Furthermore, LKDs with subclinical IF/TA tended to have decreased RRV/BW compared with those without subclinical IF/TA (P = .088).

CONCLUSIONS

Our findings suggested that the presence of IF/TA could be a predictive factor for RRF after DN. Further research establishing the predictive model for RRF is warranted to improve the outcomes of LKDs.

Contrast-enhanced MRI for simultaneous evaluation of renal morphology and split renal function in living kidney donor candidates

PURPOSE

The evaluation process of potential living kidney donors focusses on renal anatomy and split renal function. This study aimed to evaluate a magnetic resonance imaging (MRI)-based approach for simultaneous evaluation of both and its impact on clinical decision making.

METHOD

Over a 3-year period, 65 potential living kidney donors were consecutively enrolled. The MRI protocol was extended by MR-nephrography to measure split renal function. Standard DTPA-scintigraphy was used for functional comparison.

RESULTS

Split renal function showed no systematic bias between the two methods (mean difference 0.3%, p = 0.08). Both methods would have yielded the same clinical decision for donor nephrectomy in 75% of the patients. In 25 % of the patients, one method indicated a relevant side difference while the other did not, and a different clinical decision could have been made based on split renal function alone.

CONCLUSIONS

MRI proved eligible for comprehensive living kidney donor evaluation and non-inferior to scintigraphy for determining split renal function. In clinical decision making, these two methods would have resulted in the same side for donor nephrectomy in a large proportion of potential donors. Whether MRN will be implemented in clinical practice depends on transplant centre infrastructure and policy.

The impact of measuring split kidney function on post-donation kidney function: A retrospective cohort study

Background

Studies have reported agreement between computed tomography (CT) and renography for the determination of split kidney function. However, their correlation with post-donation kidney function remains unclear. We compared CT measurements with renography in assessment of split kidney function (SKF) and their correlations with post-donation kidney function.

Methods

A single-centre, retrospective cohort study of 248 donors from January 1, 2009-July 31, 2019 were assessed. Pearson correlations were used to assess post-donation kidney function with renography and CT-based measurements. Furthermore, we examined high risk groups with SKF difference greater than 10% on renography and donors with post-donation eGFR less than 60 mL/min/1.73m².

Results

62% of donors were women with a mean (standard deviation) pre-donation eGFR 99 (20) and post-donation eGFR 67 (22) mL/min/1.73m² at 31 months of follow-up. Post-donation kidney function was poorly correlated with both CT-based measurements and renography, including the subgroup of donors with post-donation eGFR less than 60 mL/min/1.73m² (r less than 0.4 for all). There was agreement between CT-based measurements and renography for SKF determination (Bland-Altman agreement [bias, 95% limits of agreement] for renography vs: CT volume, 0.76%, -7.60–9.15%; modified ellipsoid,1.01%, -8.38–10.42%; CC dimension, 0.44%, -7.06–7.94); however, CT missed SKF greater than 10% found by renography in 20 out 26 (77%) of donors.

Conclusions

In a single centre study of 248 living donors, we found no correlation between CT or renography and post-donation eGFR. Further research is needed to determine optimal ways to predict remaining kidney function after donation.

Determination of split renal function in voluntary renal donors by multidetector computed tomography and nuclear renography: How well do they correlate?

Background

The use of computed tomography (CT) for estimation of split renal function (SRF) has been reported previously. However, most of these studies have small samples, and many do not account for the renal attenuation at CT.

Objective

The aim of this study was to compare multidetector computed tomography (MDCT) volumetry-attenuation-based SRF with that obtained via Tc99m-diethylenetriaminepentaacetic acid (DTPA) renal scintigraphy in voluntary renal donors.

Methods

Between January 2017 and January 2020, 526 voluntary renal donors were enrolled prospectively. All donors underwent contrast CT and DTPA scan before surgery. The semiautomatic region of interest (ROI) tool was applied slice by slice on axial CT images acquired in the arterial phase. The renal contour was drawn semiautomatically with mouse clicks around the renal parenchyma, and the renal volume was ascertained. Using renal volume and attenuation, SRF was determined and compared with results obtained at DTPA imaging.

Results

The mean age was 44.91 ± 10.97 years (mean ± s.d.). There was no significant difference in SRF based on DTPA and MDCT volumetry for the left kidney (49.18% ± 3.40% vs. 49.15% ± 3.38%, p = 0.540) and for the right kidney (50.82% ± 3.40% vs. 50.86% ± 3.39%, p = 0.358). A very good correlation was observed between the two methods for the left kidney (r = 0.953, p = 0.000) and the right kidney (r = 0.955, p = 0.000). On simple linear regression analysis, 90.8% of DTPA SRF values for the left kidney and 91.3% of DTPA SRF values for the right kidney could be predicted correctly using the corresponding MDCT SRF values.

Conclusion

MDCT volumetry-attenuation-derived estimation of SRF for living renal donors could be an alternative to renal scintigraphy-based SRF estimation.

Assessment of Split Renal Function Using a Combination of Contrast-Enhanced CT and Serum Creatinine Values for Glomerular Filtration Rate Estimation

OBJECTIVE. The objective of our study was to develop a novel method to estimate single-kidney glomerular filtration rate (GFR) using a combination of contrast-enhanced CT and serum creatinine (SCr) values and to validate the resulting estimated glomerular filtration rates (eGFRs) by comparing them with the single-kidney Gates GFR, which is based on renal dynamic imaging. MATERIALS AND METHODS. Sixty-two patients with asymmetric renal disease who underwent unenhanced and triphasic contrast-enhanced CT of the kidneys, ^99mTc-diethylenetriamine pentaacetic acid renal dynamic imaging, and SCr testing within 1 week were retrospectively included. The eGFR was split into single-kidney GFRs of the left and right kidneys by a proportionality factor derived from the products of renal volume and CT number increments of the multiphasic CT images, which produced unenhanced phase (yielded by the renal volume proportional factor alone), arterial phase, venous phase, and nephrographic phase CT split eGFRs. The four CT split eGFRs were compared with the Gates GFR using the paired-sample t test, Pearson correlation analysis, and Bland-Altman analysis. RESULTS. Correlation coefficients and 95% CIs between the four CT split eGFRs and Gates GFR were as follows: unenhanced phase, 0.729 (95% CI, 0.626-0.805); arterial phase, 0.781 (95% CI, 0.685-0.849); venous phase, 0.788 (95% CI, 0.690-0.839); and nephrographic phase, 0.842 (95% CI, 0.758-0.902) (all, p < 0.001). The paired differences between the CT split eGFRs and Gates GFR were as follows: unenhanced phase, 2.04 ± 10.85 (95% CI, 0.01-4.07) mL/min/1.73 m²; arterial phase, 2.04 ± 10.56 (95% CI, 0.06-4.02) mL/min/1.73 m²; venous phase, 2.04 ± 10.04 (95% CI, 0.16-3.92) mL/min/1.73 m²; and nephrographic phase, 2.04 ± 8.92 (95% CI, 0.37-3.71) mL/min/1.73 m². These results suggest a maximum deviation from the Gates GFR of ± 44.9% for the unenhanced phase eGFR, ± 43.7% for the arterial phase eGFR, ± 41.6% for the venous phase eGFR, and ± 36.9% for nephrographic phase eGFR. CONCLUSION. Split renal function can be estimated using a combination of contrast-enhanced CT and SCr values to calculate eGFR. The CT images of the nephrographic phase may be the optimal choice to use in this proposed method.

Semiautomated Renal Cortex Volumetry in Multislice Computed Tomography: Effect of Slice Thickness and Iterative Reconstruction Algorithms

OBJECTIVE

The aim of the study was to evaluate the effect of slice thickness, iterative reconstruction (IR) algorithm, and kernel selection on measurement accuracy and interobserver variability for semiautomated renal cortex volumetry (RCV) with multislice computed tomography (CT).

METHODS

Ten patients (62.4 ± 17.2 years) undergoing abdominal biphasic multislice computed tomography were enrolled in this retrospective study. Computed tomography data sets were reconstructed at 1-, 2-, and 5-mm slice thickness with 2 different IR algorithms (iDose, IMRST) and 2 different kernels (IMRS and IMRR) (Philips, the Netherlands). Two readers independently performed semiautomated RCV for each reconstructed data set to calculate left kidney volume (LKV) and split renal function (SRF). Statistics were calculated using analysis of variance with Geisser-Greenhouse correction, followed by Tukey multiple comparisons post hoc test. Statistical significance was defined as P ≤ 0.05.

RESULTS

Semiautomated RCV of 120 data sets (240 kidneys) was successfully performed by both readers. Semiautomated RCV provides comparable results for LKV and SRF with 3 different slice thicknesses, 2 different IR algorithms, and 2 different kernels. Only the 1-mm slice thickness showed significant differences for LKV between IMRR and IMRS (P = 0.02, mean difference = 4.28 bb) and IMRST versus IMRS (P = 0.02, mean difference = 4.68 cm) for reader 2. Interobserver variability was low between both readers irrespective of slice thickness and reconstruction algorithm (0.82 ≥ P ≥ 0.99).

CONCLUSIONS

Semiautomated RCV measurements of LKV and SRF are independent of slice thickness, IR algorithm, and kernel selection. These findings suggest that comparisons between studies using different slice thicknesses and reconstruction algorithms for RCV are valid.

Split renal function in patients with renal masses: utility of parenchymal volume analysis vs nuclear renal scans

OBJECTIVES

To evaluate the utility of parenchymal volume analysis (PVA) for estimation of split renal function (SRF) in patients with renal masses. SRF is important for deciding about partial vs radical nephrectomy (PN/RN) and assessing risk for developing severe chronic kidney disease after surgery. For renal donors PVA is routinely used to estimate SRF, but the utility of PVA for the more complex renal mass population remains undefined.

PATIENTS AND METHODS

All patients (n = 374) with renal tumours and a normal contralateral kidney managed with PN (2010-2018), with preoperative/postoperative nuclear renal scans (NRS) and cross-sectional imaging were analysed. Parenchymal volumes were measured by free-hand scripting or software analysis. Concordance between ipsilateral estimated glomerular filtration rate (eGFR) values based on SRF from NRS vs PVA were evaluated by Pearson correlation and Bland-Altman plots. Parallel analysis of all 155 patients managed with RN at our centre (2006-2016) with preoperative NRS and imaging was also performed.

RESULTS

For PN, the median age and tumour size were 62 years and 3.4 cm, respectively. The median preoperative ipsilateral parenchymal volume and eGFR were 181 cm³ and 36.9 mL/min/1.73 m² , respectively. Parenchymal volumes estimated by free-hand scripting vs software analyses correlated strongly (r = 0.98, P < 0.001). Preoperative ipsilateral eGFR based on SRF from PVA vs NRS also correlated strongly (r = 0.94, P < 0.001). Ipsilateral eGFR saved after PN correlated strongly with parenchymal volume preserved (all r >0.60); however, the correlation was much stronger when ipsilateral eGFRs were based on SRF from PVA rather than NRS (z-statistic = 3.15, P = 0.002). For RN patients, preoperative eGFR in the contralateral kidney based on SRF from PVA vs NRS also correlated strongly (r = 0.87, P < 0.001).

CONCLUSION

PVA has utility for estimation of SRF in patients with renal masses, even though this population is older and more comorbid than renal donors and the tumour can complicate the analysis. PVA can be obtained by software analysis from preoperative cross-sectional imaging and thus readily incorporated into routine clinical practice.

Can Split Renal Volume Assessment by Computed Tomography Replace Nuclear Split Renal Function in Living Kidney Donor Evaluations? A Systematic Review and Meta-Analysis

Background:

As part of their living kidney donor assessment, all living donor candidates complete a computed tomography (CT) angiogram, but some also receive a nuclear renogram for split renal function (SRF%).

Objective:

We considered whether split renal volume (SRV%) assessed by CT can predict SRF%.

Design:

Systematic review and meta-analysis.

Setting:

Living donor candidates undergoing evaluation as potential living kidney donors.

Patients:

Living donor candidates who received both a nuclear renogram for split function and CT for SRV as part of their living donor work-up.

Measurements:

Split renal volume from CT scans and SRF from nuclear renography.

Methods:

We performed a systematic review and meta-analysis of the literature, abstracting data and digitizing plots where possible. We searched Medline, EMBASE, and the Cochrane Library. We added data from donor candidates assessed in London, Ontario from 2013 to 2016. We used fixed and random-effects models to pool Fisher’s z-transformed Pearson’s correlation coefficient (r). We conducted random-effects meta-regression on digitized and aggregate data. Studies were restricted to living kidney donors or living donor candidates.

Results:

After pooling 19 studies (n = 1479), we obtained a pooled correlation of r = 0.74 (95% confidence interval [CI] = 0.61-0.82). By linear regression using individual-level data, we observed a 0.76% (95% CI = 0.71-0.81) increase in SRF% for every 1% increase in SRV%. Split renal volume had a specificity of 88% for discriminating SRF at a threshold that could influence the decision of which kidney is to be removed (between-kidney difference ≥10%). Predonation SRV and SRF both moderately predicted kidney function 6 to 12 months after donation: r = 0.75 for SRV and r = 0.73 for SRF; Δr = 0.05 (–0.02, 0.13).

Limitations:

Most studies were retrospective and measured SRV and SRF only on selected living donor candidates. Efficiency gains in removing the SRF from the evaluation will depend on the transplant program.

Conclusion:

Split renal volume has the potential to replace SRF for some candidates. However, it is uncertain whether it can do so reliably and routinely across different transplant centers. The impact on clinical decision-making needs to be assessed in well-designed prospective studies.

Trial registration:

The digitized data are registered with Mendeley Data (doi10.17632/dyn2bfgxxj.2).

Preserved Kidney Volume, Body Mass Index, and Age Are Significant Preoperative Factors for Predicting Estimated Glomerular Filtration Rate in Living Kidney Donors at 1 Year After Donation

BACKGROUND

Securing postdonation renal function in the lifetime of donors is a consequential subject for physicians, and precise prediction of postdonation renal function would be considerably beneficial when judging the feasibility of kidney donation. The aim of this study was to investigate the optimum model for predicting eGFR at 1 year after kidney donation.

METHODS

We enrolled 101 living-related kidney donors for the development cohort and 44 for the external validation cohort. All patients in each cohort underwent thin-sliced (1 mm) enhanced computed tomography (CT) scans. We excluded individuals with diabetes, glucose intolerance, or albuminuria from this study. We evaluated preoperative factors including age, sex, hypertension, body mass index (BMI), serum uric acid, baseline eGFR, and body surface area (BSA)-adjusted preserved kidney volume (PKV) by using 3-dimensional reconstruction of thin-sliced enhanced CT images. To detect independent predictors, we performed multivariable regression analysis.

RESULTS

The multivariable regression analysis revealed that age, BMI, predonation eGFR, and BSA-adjusted PKV were independent predictors of eGFR at 1 year after kidney donation (correlation coefficient: -0.15, -0.476, 0.521, 0.127, respectively). A strong correlation between predicted eGFR and observed eGFR was obtained in the development cohort (r = 0.839, P < .0001). The significance of this predictive model was also confirmed with the external validation cohort (r = 0.797, P < .0001).

CONCLUSIONS

Age, BMI, predonation eGFR, and BSA-adjusted PKV may be useful for precisely predicting eGFR at 1 year after living kidney donation and be helpful to determine the feasibility of kidney donation from marginal donors.

Role of Computed Tomography Volumetry in Preoperative Donor Renal Function Evaluation of Living Related Kidney Transplantation

INTRODUCTION

Renal scintigraphy is used to evaluate split renal function. A computed tomography (CT) examination is also carried out for donor safety and appropriate transplantation surgery, and the renal volume (CT volumetry) can be obtained at that time. In this study, we evaluated donor kidney function by inulin clearance (Cin) before and after donor nephrectomy in living donor renal transplantation, and the predictive role of CT volumetry was compared with diethylenetriamine pentaacetic acid (DTPA).

METHOD

From November 2005 to April 2018, 34 cases of living donor transplantation conducted at Fukuoka University Hospital were retrospectively studied. The donated kidney weight was measured in 25 cases, and postoperative Cin was measured in 19 cases.

RESULTS

The average donor age was 51.7 years old (from 35 to 71). Preoperative Cin and postoperative Cin of donors were 86.3 mL/min/1.73 m² (from 59.5 to 138.3) and 52.3 (from 40.5 to 76.6), respectively. The average CT volumetry of donated kidneys was 153.9 mL (from 107.8 to 219.3). Correlations of weight and DTPA and CT volumetry of donated kidneys were r = 0.033 (P = .8770) and r = 0.763 (P < .0001), respectively. Correlations of glomerular filtration rate of DTPA and CT volumetry and Cin of postoperative donor residual kidneys were r = 0.66 (P = .002) and r = 0.555 (P = .014).

CONCLUSION

There was a significant correlation between CT volumetry and the weight of the removed kidneys, and a correlation between Cin after donor nephrectomy and CT volumetry of the remaining kidneys, but it did not exceed the predictive role of DTPA. However, it was suggested that it is worthy to use as a preoperative examination for split renal function equivalent to DTPA.

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.

The 3-D Volumetric Measurement Including Resected Specimen for Predicting Renal Function AfterRobot-assisted Partial Nephrectomy

OBJECTIVE

To investigate the relationship between postoperative renal function and resected cortex margin volume calculated by a 3-dimensional reconstruction technique based on the resected specimen, and to determine predictors of renal function after robot-assisted partial nephrectomy.

METHODS

A total of 114 patients underwent robot-assisted partial nephrectomy from 2014 to 2018. Patients without a 1 mm slice computed tomography or renal scintigraphy were excluded. We identified the margins of the tumor from each resected specimen with 2 mm margin being added as the ischemic margin. The volume of the renal cortex was calculated automatically using 3-dimensional volume analyzer software. The total margin volume was excluded from the ipsilateral cortex volume to calculate the cortex volume split. Predicted estimated glomerular filtration rate (eGFR) was calculated using the change in cortex volume and then compared with the actual eGFR.

RESULTS

Eighty-two patients were included in this retrospective study. Sixty-six patients (80%) were cT1a. A strong correlation was observed between renal scintigraphy split and pre- and postoperative cortex volume split (Pearson correlation coefficient r = 0.9330 and 0.8742, respectively). The predicted eGFR correlated strongly with post 1, 3, 6, and 12 months eGFR (r = 0.8929, 0.9294, 0.9320, and 0.8952, respectively). Preoperative relative renal function and total cortex margin volume were independent risk factors for decreasing postoperative renal function.

CONCLUSION

This precise volumetric assessment that includes the resected margin is an alternative to renal scintigraphy for predicting postoperative relative renal function. The healthy cortex margin volume calculated by the reconstruction technique is an independent risk factor of decreasing postoperative renal function.

Donor kidney volume measured by computed tomography is a strong predictor of recipient eGFR in living donor kidney transplantation

PURPOSE

The effect of living donor kidney allograft size on recipient outcomes is not well understood. In this study, we sought to investigate the relationship between preoperatively measured donor kidney volume and recipient estimated glomerular filtration rate (eGFR) in living donor kidney transplantation (LDKT).

METHODS

We studied computed tomography (CT) donor kidney volumes and recipient outcomes for 438 LDKTs at the Toronto General Hospital between 2007 and 2016. Estimated glomerular filtration rate (eGFR) was calculated at 1, 3, and 6 months and a multivariable linear regression model was fitted to study the effect of donor kidney volume on recipient eGFR.

RESULTS

The mean volume and weight of the donated kidneys were 157.3 (± 32.3) cc and 186.7 (± 48.7) g, respectively. Kidney volume was significantly associated with eGFR on multivariable analysis (P < 0.001). Specifically, for every 10 cc increase in kidney volume, there was a 1.68 mL/min, 1.25 mL/min and 0.97 mL/min rise in recipient eGFR at 1, 3, and 6 months, respectively.

CONCLUSIONS

Donor kidney volume is a strong independent predictor of recipient eGFR in LDKT, and therefore, may be a valuable addition to predictive models of eGFR after transplant. Further research may determine if the inclusion of donor kidney volume in matching algorithms can improve recipient outcomes.

Scintigraphic texture analysis for assessment of renal allograft function

Purpose

Early detection and monitoring of kidney function during the post-transplantation period is one of the most important issues for improving the accuracy of an initial diagnosis. The aim of this study was to evaluate texture analysis (TA) in scintigraphic imaging to detect changes in kidney status after transplantation.

Material and methods

Scintigraphic images were used for TA from a total of 94 kidney allografts (39 rejected and 55 non-rejected). Images corresponding to the frames at the 2^nd, 5^th, and 20^th minute of the study were used to determine the optimum time point for analysis of differences in texture features between the rejected and non-rejected allografts.

Results

Linear discriminant analysis indicated the best performance at the fifth minute frame for classification of the rejected and non-rejected allografts with receiver operating characteristic curve (A_z) of 0.982, corresponding to 91.89% sensitivity, 96.49% specificity, and 94.68% accuracy. Also, TA can differentiate acute tubular necrosis from acute rejection with A_z of 0.953 corresponding to 88% sensitivity, 92.31% specificity, and 90.62% accuracy at the 5^th minute frame. The best correlation between texture feature and kidney function was achieved at the 20^th minute frame (r = -0.396) for glomerular filtration rate.

Conclusions

TA has good potential for the characterisation of kidney failure after transplantation and can improve clinical diagnosis.

Renal cortical volume: High correlation with pre- and post-operative renal function in living kidney donors

BACKGROUND

CT volumetry has previously been proposed as an alternative to scintigraphy for the evaluation of pre-donation split renal function and the prediction of post-donation renal function in living kidney donors. The aim of our study was to retrospectively assess the relevance of three CT volumetry techniques for estimating pre-donation kidney function and predicting the risk for chronic kidney disease (CKD) at 1-year post-nephrectomy in a French cohort of living donors using isotopic measures of kidney function.

METHODS

Kidney volume was quantified pre-donation for 105 donors using three methods total parenchymal three-dimensional renal volume (3DRV), total parenchymal renal volume contouring (RVCt), and renal cortical volume (RCoV). Subjects also had a 51Cr-EDTA scintigraphy to measure glomerular filtration rate (mGFR) pre-donation and 1-year after donation. For each volume, we tested for association with mGFR using univariate regression models, and computed receiver operating characteristics analyses to assess their predictive potential of post-donation CKD.

RESULTS

Our population was composed of healthy subjects, who were predominantly female (69%) with a median age at donation of 51yo. Median mGFR was 102 mL/min/1.73 m² at pre-donation and 66 mL/min/1.73 m² 1-year after nephrectomy. The pre-donation median volume of the preserved kidney was 156 cm³, 163 cm³ and 99 cm³ for the 3DRV, RVCt and RCoV methods respectively, with a high correlation observed between each technique (R > 0.84). For all methods, total kidney volume was significantly associated with pre-donation mGFR (P < 0.001). Preserved kidney volume was also strongly correlated with post-donation mGFR (P < 0.0001), with the strongest correlation observed for RCoV (R = 0.60 vs. R = 0.39 and R = 0.51 for 3DRV and RVCt, respectively). Finally, the RCoV method yielded the best predictive value of 1-year post-donation CKD (AUC = 0.80 vs. AUC = 0.76 and 0.70 for RVCt and 3DRV, respectively).

CONCLUSIONS

In our cohort of healthy donors with measured kidney function, cortical volumetry (RCoV) appears as the best volumetric technique to use as a surrogate to scintigraphy for estimating pre-donation split renal function and predicting post-donation renal outcomes.