Estimation of split renal function using different volumetric methods: inter- and intraindividual comparison between MRI and CT

Non-contrast-enhanced magnetic resonance urography for measuring split kidney function in pediatric patients with hydronephrosis: comparison with renal scintigraphy

BACKGROUND

Split kidney function (SKF) is critical for treatment decision in pediatric patients with hydronephrosis and is commonly measured using renal scintigraphy (RS). Non-contrast-enhanced magnetic resonance urography (NCE-MRU) is increasingly used in clinical practice. This study aimed to investigate the feasibility of using NCE-MRU as an alternative to estimate SKF in pediatric patients with hydronephrosis, compared to RS.

METHODS

Seventy-five pediatric patients with hydronephrosis were included in this retrospective study. All patients underwent NCE-MRU and RS within 2 weeks. Kidney parenchyma volume (KPV) and texture analysis parameters were obtained from T2-weighted (T2WI) in NCE-MRU. The calculated split KPV (SKPV) percent and texture analysis parameters percent of left kidney were compared with the RS-determined SKF.

RESULTS

SKPV showed a significant positive correlation with SKF (r = 0.88, p < 0.001), while inhomogeneity was negatively correlated with SKF (r =  - 0.68, p < 0.001). The uncorrected and corrected prediction models of SKF were established using simple and multiple linear regression. Bland-Altman plots demonstrated good agreement of both predictive models. The residual sum of squares of the corrected prediction model was lower than that of the uncorrected model (0.283 vs. 0.314) but not statistically significant (p = 0.662). Subgroup analysis based on different MR machines showed correlation coefficients of 0.85, 0.95, and 0.94 between SKF and SKPV for three different scanners, respectively (p < 0.05 for all).

CONCLUSIONS

NCE-MRU can be used as an alternative method for estimating SKF in pediatric patients with hydronephrosis when comparing with RS. Specifically, SKPV proves to be a simple and universally applicable indicator for predicting SKF.

What are the Optimal Renal Ultrasound Parameters for Detecting Small Kidney in Young Children?

Introduction

Recent guidelines do not recommend routine screening of vesicoureteral reflux after a first febrile urinary tract infection in children without abnormal findings on ultrasound or atypical/recurrent urinary tract infection. Currently, there are no clear ultrasonographic parameters for detecting abnormalities in renal size, especially in young children. The aim of the present study was to determine an optimal cutoff value for detecting small kidney in children without apparent congenital anomalies except vesicoureteral reflux by retrospective chart review.

Patients and Methods

Children aged ≤3 years who had undergone nuclear renal scans and ultrasound were enrolled. Small kidney was defined as split renal function of <40%. Optimal cutoff values of various ultrasonographic parameters for detecting small kidney were calculated.

Results

Of the 69 children included in the present study, small kidney was identified in 20. There was a significant difference in renal size between each kidney in patients with small kidney, whereas there was no significant difference in those without small kidney. With a ratio of estimated renal area of 74.26%, maximum area under the curve with the highest sensitivity, specificity, positive predictive value, negative predictive value, and accuracy rate were obtained. In addition, simple measurement of renal length with a cutoff of 4.97 cm showed high specificity comparable with estimated renal area.

Conclusion

Small kidney may be screened by two-dimensional measurement on ultrasonographic examination, even in young children. With the cutoff described, risk stratification or an individualized approach may be possible.

[Living donor nephrectomy: The French guidelines from CTAFU]

OBJECTIVE

To propose surgical recommendations for living donor nephrectomy.

METHOD

Following a systematic approach, a review of the literature (Medline) was conducted by the CTAFU regarding functional and anatomical assessment of kidney donors, including which side the kidney should be harvested from. Distinct surgical techniques and approaches were evaluated. References were considered with a predefined process to propose recommendations with the corresponding levels of evidence.

RESULTS

The recommendations clarify the legal and regulatory framework for kidney donation in France. A rigorous assessment of the donor is one of the essential prerequisites for donor safety. The impact of nephrectomy on kidney function needs to be anticipated. In case of modal vascularization of both kidneys without a relative difference in function or urologic abnormality, removal of the left kidney is the preferred choice to favor a longer vein. Mini-invasive approaches for nephrectomy provide faster donor recovery, less donor pain and shorter hospital stay than open surgery.

CONCLUSION

These French recommendations must contribute to improving surgical management of candidates for kidney 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.

A prospective study of novel mathematical analysis of the contrast-enhanced computed tomography vs renal scintigraphy in renal function evaluation

PURPOSE

whilst renal scintigraphy (RS) can be associated with interobserver variability, it remains the standard method of evaluating split renal function.

AIM

to compare the efficacy of the novel technique of kidney function assessment and renal scintigraphy.

METHOD

for this prospective single-arm study we recruited patients who were recommended dynamic renal scintigraphy with ⁹⁹mTc-DTPA (diethylenetriaminepentacetate). After scintigraphy, mathematical analysis of computed tomography (MACT) was done in all patients, by a single person (SK) blinded to RS results.

RESULTS

the study included a total of 97 patients with mean age of 50.9 (range, 23-78) years. From this sample, 65 were females and 32 males. All patients underwent both RS and contrast-enhanced computed tomography for further MACT in 2016-2018. CT results were found to be similar to renal scintigraphy results with Pearson correlation coefficient of 0.945 (р < 0.001). Substantial similarities in renal plasma flow for both kidneys were also observed (0.815, р < 0.001).

CONCLUSION

MACT proved feasible, effective and safe in estimating renal function. Its results are closely correlated with RS findings and could be easily integrated into surgical practice.