Luglio Agosto 2023 - Articoli originali

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


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.

  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


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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