Correlation of Acoustic Radiation Force Impulse Imaging with Chronicity Markers in Native Renal Biopsy

Abstract

Introduction. Acoustic Radiation Force Impulse (ARFI) is an ultrasound parameter which has shown promise in assessing liver stiffness, but there are limited data on the correlation of ARFI with chronicity markers in renal biopsies.
Objectives.

  1. Determine ARFI values in ultrasound and correlate with chronicity markers in renal biopsy
  2. Determine whether ARFI can be used as a non-invasive chronicity predictor compared to renal length, Resistive Index (RI), and cortical thickness.

Patients and Methods. Two hundred and fifty patients were enrolled in the study. The ultrasound variables ARFI, renal length, RI, and cortical thickness values were assessed by the radiologist prior to renal biopsy. The biopsy slides were graded as per the Mayo Clinic consensus report scoring system by an experienced pathologist.
Results. Among 250 study participants, 167 were males and 83 were females. IgA nephropathy was the most common pathology (n=47;19%), followed by diabetic nephropathy (n=42;17%), membranous nephropathy (n=35;14%), FSGS (n=27;11%), and MCD (n=19; 8%). The mean eGFR was 55.9 ± 42.12 ml/min/1.73 m2. The average renal length was 10.086 ± 1.01 cm. The average cortical thickness was 0.707 ± 0.134 cm. Resistive index was 0.68 ± 0.09. Acoustic radiation force impulse had weak negative correlation (r=-0.286; p=0.0001) with total pathological score and weak positive correlation with eGFR (r=0.279; p=0.0001). RI was a better indicator for histologically evaluated chronicity with positive correlation coefficient (r=0.416; p=0.0005) compared to renal length, cortical thickness, and ARFI.
Conclusion. ARFI didn’t corelate with the pathological score in renal biopsies. RI had better predictive value for chronicity in native renal biopsies.

Keywords: ARFI, Resistive index, Cortical thickness, Renal length, Chronicity

Introduction

Chronic Kidney Disease (CKD) is a vexing global health issue, with its reported prevalence in India ranging from 1% to 13% [1]. Renal biopsy is considered the gold standard to assess the extent of glomerulosclerosis, interstitial fibrosis, tubular atrophy, and vascular sclerosis which influence the progression of CKD [1]. In low- to middle-income countries, biopsy assessment and the technical prowess for kidney biopsy are not easily accessible. Acoustic Radiation Force Impulse Imaging (ARFI) is a unique ultrasound technique which superimposes data involving tissue elasticity onto ultrasound-produced greyscale images. It has been found to be highly useful in assessing liver, breast, prostate, and thyroid pathologies [2, 3]. ARFI uses short-duration, brief focused acoustic pulses along the main ultrasound beam to induce tissue shear stress, which is dependent on tissue attenuation, acoustic beam intensity, and acoustic frequency [2]. These shear stresses are converted into shear waves whose speed is directly proportional to the density and elasticity of the tissue [2]. ARFI has been used previously in chronicity evaluation in kidney biopsy samples [2]. The majority of the studies [3] state that ARFI doesn’t correlate with renal histological fibrosis, but a single study [2] mentions that ARFI correlates with histological renal fibrosis in chronic kidney disease with a sensitivity of 86% and specificity of 82%. Resistive index (RI) has been previously reported to correlate well with glomerulosclerosis, vascular sclerosis, and interstitial fibrosis in renal biopsies [4]. Renal length and cortical thickness have proved to be sensitive parameters for predicting chronicity and progression in chronic kidney disease and had a good correlation with estimated glomerular filtration rate (eGFR) [5, 6]. There is a paucity of South Asian data on the correlation of ARFI with chronicity markers in renal biopsies irrespective of aetiology and hence this study was designed to mitigate this research gap. 

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Quantitative imaging in nephrology: limits and potentials of elastosonography

Abstract

Chronic kidney disease is characterized by increasingly amplified fibrotic processes regardless of etiology. The severity of renal fibrosis seems to correlate with an increased risk of end-stage renal disease; therefore, monitoring of renal fibrosis over time may play an important role in the follow-up of both focal and diffuse renal diseases and in evaluating the response to treatments. Renal biopsy is the only method capable of providing objective and comparable information on the extent of fibrosis, but it is not suitable for outpatient monitoring of chronic kidney disease due to its invasiveness. Elastosonography is an innovative and non-invasive ultrasound method that allows the measurement of tissue elasticity through the transmission of mechanical waves and the measurement of their propagation speed. Although some authors have demonstrated the usefulness of elastosonographic techniques for the quantification of liver fibrosis, few studies have investigated the applications of elastosonography in renal pathology. Furthermore, the depth of native kidneys, the high anisotropy of the renal tissue, and the possibility of examining only a small region of interest currently limit its spread in clinical practice. The aim of this review is to examine the physical principles of elastosonography and to review the latest evidence about the possible applications of the ARFI (acoustic radiation force impulse) technique in the study of kidney diseases.

Keywords: ultrasound, fibrosis, renal elastosonography, ARFI, quantitative imaging

Sorry, this entry is only available in Italian.

Introduzione

La malattia renale cronica (Chronic Kidney Disease, CKD) è una condizione patologica ad elevata prevalenza nella popolazione generale, caratterizzata da alterazioni della funzione renale e/o anomalie strutturali presenti per più di tre mesi, con variabile tendenza alla progressione verso forme più gravi di insufficienza d’organo [1]. Sebbene numerose patologie del parenchima, dei vasi o delle vie escretrici (sia primitive che secondarie) possano provocare la CKD, la fibrosi d’organo rappresenta la caratteristica comune a tutti i differenti meccanismi patogenetici responsabili di danno renale. Il grado di fibrosi sembra inoltre essere correlato con un maggior rischio di progressione verso l’End Stage Renal Disease (ESRD), pertanto possiede un elevato valore predittivo negativo per l’outcome delle patologie renali croniche [2]. 

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