Diffusion-weighted imaging of the kidneys in haemolytic uraemic syndrome

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.

Consensus-based technical recommendations for clinical translation of renal diffusion-weighted MRI

Objectives

Standardization is an important milestone in the validation of DWI-based parameters as imaging biomarkers for renal disease. Here, we propose technical recommendations on three variants of renal DWI, monoexponential DWI, IVIM and DTI, as well as associated MRI biomarkers (ADC, D, D*, f, FA and MD) to aid ongoing international efforts on methodological harmonization.

Materials and methods

Reported DWI biomarkers from 194 prior renal DWI studies were extracted and Pearson correlations between diffusion biomarkers and protocol parameters were computed. Based on the literature review, surveys were designed for the consensus building. Survey data were collected via Delphi consensus process on renal DWI preparation, acquisition, analysis, and reporting. Consensus was defined as ≥ 75% agreement.

Results

Correlations were observed between reported diffusion biomarkers and protocol parameters. Out of 87 survey questions, 57 achieved consensus resolution, while many of the remaining questions were resolved by preference (65–74% agreement). Summary of the literature and survey data as well as recommendations for the preparation, acquisition, processing and reporting of renal DWI were provided.

Discussion

The consensus-based technical recommendations for renal DWI aim to facilitate inter-site harmonization and increase clinical impact of the technique on a larger scale by setting a framework for acquisition protocols for future renal DWI studies. We anticipate an iterative process with continuous updating of the recommendations according to progress in the field.

Electronic supplementary material

The online version of this article (10.1007/s10334-019-00790-y) contains supplementary material, which is available to authorized users.

An equation to estimate the renal cortex volume in chronic kidney disease patients

BACKGROUND

The renal cortex volume is associated with the kidney function and chronic kidney disease (CKD) risk factors, and it may also be a prognostic factor. We aimed to create an equation to estimate the renal cortex volume of CKD patients in day-to-day clinical practice.

METHODS

The subjects included 116 ethnic Japanese CKD patients who were ≥ 18 years of age. The renal size (length, width and thickness) was measured by ultrasound. The body height, weight, year of age, sex, birth weight, gestational age, diabetes status, hypertension status, family history of CKD and dialysis and estimated glomerular filtration rate (eGFR) were collected as expected dependent variables. We made models for the equation regarding the renal cortex volume measured by non-contrast magnetic resonance imaging as a true renal cortex volume. Stepwise multiple linear regression analyses were performed with the log-transformation of dependent and independent variables. The accuracy of the models was compared using the leave one out cross-validation method.

RESULTS

The estimated volume of the renal cortex (cm³) = 0.012 × renal length (cm)^0.92 × width (cm)^0.53 × body weight (kg)^0.40 × body height (cm)^0.67 × eGFR (ml/min/1.73 m²)^0.22 × 1.12 if diabetes. The adjusted R ² value and the accuracy within 30 and 50% were 0.73, 0.94 and 0.99, respectively.

CONCLUSIONS

This study provided a new method for estimating the renal cortex volume in day-to-day clinical practice.