Renal impairment

Comparison of Shear Wave Elastography Measurements in Chronic Kidney Disease Patients and Healthy Volunteers

To evaluate renal parenchymal stiffness using 2D shear wave elastography (SWE) in patients with chronic kidney disease (CKD) and to investigate the correlation between SWE results and demographic as well as laboratory findings. We evaluated 41 CKD patients and 40 controls who underwent abdominal ultrasound (US) between December 2020 and November 2022. SWE measurements were performed by a single radiologist, assessing renal stiffness in the lower pole, middle section, and upper pole of each kidney. The mean stiffness values were calculated from at least six measurements per kidney. Laboratory data, including glomerular filtration rate (GFR), serum urea, and creatinine levels, were obtained. Mann-Whitney U and Spearman correlation tests were used for statistical analysis. CKD patients (mean age: 66 years) showed significantly higher cortical stiffness compared with controls (15.6 kPa vs. 5.5 kPa, p < 0.001). A positive correlation was found between stiffness and serum urea/creatinine levels, while an inverse correlation was observed with GFR (p < 0.001). A negative correlation was observed between kidney size and SWE (r = -0.215, p = 0.054), while parenchymal thickness showed a stronger and statistically significant inverse relationship with SWE (r = -0.301, p = 0.006). No significant correlation was found with age or gender (p > 0.05). SWE is a reliable, noninvasive method for assessing renal fibrosis in CKD. With standardization, it could become a valuable tool in routine CKD evaluation.

Shear wave elastography in chronic kidney disease - the physics and clinical application

Chronic kidney disease is a leading public health problem worldwide. The global prevalence of chronic kidney disease is nearly five hundred million people, with almost one million deaths worldwide. Estimated glomerular filtration rate, imaging such as conventional ultrasound, and histopathological findings are necessary as each technique provides specific information which, when taken together, may help to detect and arrest the development of chronic kidney disease, besides managing its adverse outcomes. However, estimated glomerular filtration rate measurements are hampered by substantial error margins while conventional ultrasound involves subjective assessment. Although histopathological assessment is the best tool for evaluating the severity of the renal pathology, it may lead to renal insufficiency and haemorrhage if complications occurred. Ultrasound shear wave elastography, an emerging imaging that quantifies tissue stiffness non-invasively has gained interest recently. This method applies acoustic force pulses to generate shear wave within the tissue that propagate perpendicular to the main ultrasound beam. By measuring the speed of shear wave propagation, the tissue stiffness is estimated. This paper reviews the literature and presents our combined experience and knowledge in renal shear wave elastography research. It discusses and highlights the confounding factors on shear wave elastography, current and future possibilities in ultrasound renal imaging and is not limited to new sophisticated techniques.

Shear wave elastography in the evaluation of renal parenchymal stiffness in patients with chronic kidney disease

OBJECTIVE

To investigate the use of shear wave elastography (SWE)-derived estimates of Young's modulus (YM) as an indicator to detect abnormal renal tissue diagnosed by estimated glomerular filtration rate (eGFR).

METHODS

The study comprised 106 chronic kidney disease (CKD) patients and 203 control subjects. Conventional ultrasound was performed to measure the kidney length and cortical thickness. SWE imaging was performed to measure renal parenchymal stiffness. Diagnostic performance of SWE and conventional ultrasound were correlated with serum creatinine, urea levels and eGFR.

RESULTS

Pearson's correlation coefficient revealed a negative correlation between YM measurements and eGFR (r = -0.576, p < 0.0001). Positive correlations between YM measurements and age (r = 0.321, p < 0.05), serum creatinine (r = 0.375, p < 0.0001) and urea (r = 0.287, p < 0.0001) were also observed. The area under the receiver operating characteristic curve for SWE (0.87) was superior to conventional ultrasound alone (0.35-0.37). The cut-off value of less or equal to 4.31 kPa suggested a non-diseased kidney (80.3% sensitivity, 79.5% specificity).

CONCLUSION

SWE was superior to renal length and cortical thickness in detecting CKD. A value of 4.31 kPa or less showed good accuracy in determining whether a kidney was diseased or not. Advances in knowledge: On SWE, CKD patients show greater renal parenchymal stiffness than non-CKD patients. Determining a cut-off value between normal and diseased renal parenchyma may help in early non-invasive detection and management of CKD.

The renal biopsy

CONTEXT

The first renal biopsy was carried out more than a century ago, but its widespread introduction into clinical use, beginning in the 1950s, helped develop nephrology into the powerful subspecialty of internal medicine that it is today. In the past 25 years, the use of the spring-loaded biopsy gun, in combination with newer visualization techniques, including ultrasound and computed axial tomography scanning, has led to greater tissue yield and to a much lower risk of complication. During this same time, our understanding of renal pathology has increased many fold. Correct fixation and processing of renal biopsy tissue is critical, and the laboratory must be skilled with renal biopsy light microscopy, immunohistochemistry, and transmission electron microscopy preparation.

OBJECTIVES

To provide an overview of the renal biopsy, including the techniques and its complications, and to summarize proper laboratory methods for processing renal biopsy tissue.

DATA SOURCES

This article is based on a review of the literature and on the experience of the author.

CONCLUSIONS

The experienced nephropathologist, knowledgeable in both renal medicine and pathology and thus able to correlate subtle tissue-derived information with appropriate clinical data, remains the most important key to the development of an accurate clinicopathologic diagnosis.