Relationship between renal apparent diffusion coefficient values and glomerular filtration rate in infants with congenital hydronephrosis

Multiparametric quantitative renal MRI in children and young adults: comparison between healthy individuals and patients with chronic kidney disease

PURPOSE

Multiparametric quantitative renal MRI may provide noninvasive radiologic biomarkers of chronic kidney disease (CKD) based on investigations in animal models and adults. We aimed to (1) obtain normative multiparametric quantitative MRI data from the kidneys of healthy children and young adults, (2) compare MRI measurements between healthy control participants and patients with CKD, and (3) determine if MRI measurements correlate with clinical and laboratory data as well as histology.

METHODS

This was a prospective, case-control study of 20 healthy controls and 12 CKD patients who underwent percutaneous renal biopsy ranging from 12 to 23 years of age between October 2018 and March 2020. Kidney function was documented and pathology assessed for fibrosis/inflammation. Utilizing a field strength of 1.5T, we examined renal T1, T2, and T2* relaxation mapping, MR elastography (MRE), and diffusion-weighted imaging (DWI). A single analyst made all manual measurements for quantitative MRI pulse sequences. Independent measurements from cortex, medulla, and whole kidney were obtained by drawing regions of interest on single slices from the upper, mid, and lower kidney. A weighted average was calculated for each kidney; if two kidneys, the right and left were averaged. Continuous variables were compared with Mann-Whitney U test; bivariate relationships were assessed using Spearman rank-order correlation.

RESULTS

Median estimated glomerular filtration rate (eGFR) was 112.3 ml/min/1.73 m² in controls (n = 20, 10 females) and 55.0 ml/min/m² in CKD patients (n = 12, 2 females) (p < 0.0001). Whole kidney (1333 vs. 1291 ms; p = 0.018) and cortical (1212 vs 1137 ms; p < 0.0001) T1 values were higher in CKD patients. Cortical T1 values correlated with eGFR (rho = - 0.62; p = 0.0003) and cystatin C (rho = 0.58; p = 0.0007). Whole kidney (1.87 vs. 2.02 10^-3 mm²/s; p = 0.007), cortical (1.89 vs. 2.04 10^-3 mm²/s; p = 0.008), and medullary (1.87 vs. 1.98 10^-3 mm²/s; p = 0.0095) DWI apparent diffusion coefficients (ADC) were lower in CKD patients. Whole kidney ADC correlated with eGFR (rho = 0.45; p = 0.012) and cystatin C (rho = - 0.46; p = 0.009). Cortical histologic inflammation correlated with DWI ADC (rho = - 0.71; p = 0.011).

CONCLUSION

Renal T1 relaxation and DWI ADC measurements differ between pediatric healthy controls and CKD patients, correlate with laboratory markers of CKD, and may have histologic correlates.

DWI as a biomarker of renal function in children with CKD: what is the potential?

Background

Evaluation of renal microstructure is pivotal for diagnosing and monitoring chronic renal disease. DWI has been proved to be practicable and reliable examination for the assessment of renal function and parenchymal damage in some renal diseases. Our aim is to appraise DWI sequence and ADC measurement as a potential tool of renal function assessment as well as establishing a possible relationship between the different CKD stages and the renal parenchymal ADC values changes.

Results

Regarding the cause of CKD, nine patients (45%) had glomerulonephritis, 5 patients (25%) had hemolytic uremic syndrome, 2 patients (10%) had lupus nephritis, 2 patients (10%) had nepheronophthisis, and 1 patient (1.5%) had infantile nepherosis, whereas the cause of CKD was unknown in 1 patient (1.5%).

The stages of CKD were classified according to KIDGO guidelines: 6 patients (30%) were stage 1, 4 patients (20%) were stage 2, 3 patients (15%) were stage 3, 2 patients (10%) were stage 4, and 5 patients (25%) were stage 5. The patients’ group (group A) had a mean ADC value (1.85 × 10−3 ± 0.24) which was significantly lower than that of the control group (group B) (2.21 × 10−3 ± 0.12). As for the correlation between stage of CKD and ADC, we found it to be a moderate negative one with r’ value of − .655 and a significant p value of < 0.001.

Conclusion

DWI is recognized as a promising imaging tool that can take part in the assessment of the morphological and functional changes in diffuse renal parenchymal disease, hence playing an important role in the early diagnosis and staging of chronic kidney disease.

Relationship of renal apparent diffusion coefficient and functional MR urography in children with pelvicalyceal dilation

OBJECTIVE

The aim is to evaluate the age-related changes and relationship of renal apparent diffusion coefficient (ADC) against the morphological and functional changes detected by functional magnetic resonance urography (fMRU) in children with pelvicalyceal dilation, with suspected or known ureteropelvic junction obstruction.

MATERIALS AND METHODS

We retrospectively analyzed fMRUs with diffusion-weighted imaging (DWI) of the kidney in 35 subjects (25 males; median age: 7.1 years, range: 0.3-22.7 years) with 70 kidneys (40 with pelvicalyceal dilation and 30 with no pelvicalyceal dilation). Inclusion criteria were pelvicalyceal dilation, the absence of duplex kidneys and no ureteric dilation. DWI was performed with 3 diffusion gradient directions (b values = 0, 200, 500, 800 and 1,000 s/mm2). Metrics for fMRU included calyceal and renal transit times (CTT, RTT), time-to-peak (TTP), differential renal function based on volume (vDRF), Patlak number (pDRF) and combined volume and Patlak number (vpDRF). The grades of pelvicalyceal dilation, cortical thinning and corticomedullary differentiation were evaluated. The relationship between ADC values and the fMRU parameters was analyzed.

RESULTS

ADC increases with age in kidneys without pelvicalyceal dilation (R²=0.37, P<0.001). Renal ADC does not correlate with any of the morphological or fMRU parameters (P>0.07). The median ADC of kidneys without pelvicalyceal dilation was 3.73×10^-3 mm²/s (range: 2.78-5.37×0^-3 mm²/s) and the median ADC of kidneys with pelvicalyceal dilation was 3.82×10^-3 mm²/s (range: 2.70-5.70×10^-3 mm²/s). There was no correlation between ADC and the absolute differences of vDRF or pDRF (P>0.33).

CONCLUSION

Renal ADC does not correlate with morphological and functional results of fMRU changes in children with pelvicalyceal dilation due to suspected or known ureteropelvic junction obstruction.

Diffusion-weighted imaging in pediatric body magnetic resonance imaging

Diffusion-weighted MRI is being increasingly used in pediatric body imaging. Its role is still emerging. It is used for detection of tumors and abscesses, differentiation of benign and malignant tumors, and detection of inflamed bowel segments in inflammatory bowel disease in children. It holds great promise in the assessment of therapy response in body tumors, with apparent diffusion coefficient (ADC) value as a potential biomarker. Significant overlap of ADC values of benign and malignant processes and less reproducibility of ADC measurements are hampering its widespread use in clinical practice. With standardization of the technique, diffusion-weighted imaging (DWI) is likely to be used more frequently in clinical practice. We discuss the principles and technique of DWI, selection of b value, qualitative and quantitative assessment, and current status of DWI in evaluation of disease processes in the pediatric body.

Evaluation of renal allografts function early after transplantation using intravoxel incoherent motion and arterial spin labeling MRI

PURPOSE

To evaluate renal allografts function early after transplantation using intravoxel incoherent motion (IVIM) and arterial spin labeling (ASL) MRI.

METHODS

This prospective study was approved by the local ethics committee, and written informed consent was obtained from all participants. A total of 82 participants with 62 renal allograft recipients (2-4weeks after kidney transplantation) and 20 volunteers were enrolled to be scanned using IVIM and ASL MRI on a 3.0T MR scanner. Recipients were divided into two groups with either normal or impaired function according to the estimated glomerular filtration rate (eGFR) with a threshold of 60ml/min/1.73m(2). The apparent diffusion coefficient (ADC) of pure diffusion (ADCslow), the ADC of pseudodiffusion (ADCfast), perfusion fraction (PF), and renal blood flow (RBF) of cortex were compared among three groups. The correlation of ADCslow, ADCfast, PF and RBF with eGFR was evaluated. The receiver operating characteristic (ROC) curve and binary logistic regression analyses were performed to assess the diagnostic efficiency of using IVIM and ASL parameters to discriminate allografts with impaired function from normal function. P<0.05 was considered statistically significant.

RESULTS

In allografts with normal function, no significant difference of mean cortical ADCslow, ADCfast, and PF was found compared with healthy controls (P>0.05). Cortical RBF in allografts with normal function was statistically lower than that of healthy controls (P<0.001). Mean cortical ADCslow, ADCfast, PF and RBF were lower for allografts with impaired function than that with normal function (P<0.05). Mean cortical ADCslow, ADCfast, PF and RBF showed a positive correlation with eGFR (all P<0.01) for recipients. The combination of IVIM and ASL MRI showed a higher area under the ROC curve (AUC) (0.865) than that of ASL MRI alone (P=0.02).

CONCLUSION

Combined IVIM and ASL MRI can better evaluate the diffusion and perfusion properties for allografts early after kidney transplantation.