## 1 Introduction  
Chronic kidney disease (CKD) is becoming more prevalent, and its progression is linked to increased morbidity, mortality, and healthcare costs. [1] As a consequence, it is essential to diagnose CKD earlier and accurately measure the disease's progression using several markers (biomarkers, histology, imaging). The kidneys are evaluated using conventional ultrasound; however, this method only gives us a few pieces of quantifiable information regarding the renal size and parenchyma thickness, which both decrease as CKD develops. Ultrasound additionally provides us with some non-quantifiable evidence on the echogenicity of the renal cortex, which increases when fibrosis advances in the later stages of CKD when the kidneys stiffen. However, the diagnostic value of the use of conventional ultrasound in the assessment of chronic kidney disease is limited [2]. The diagnostic accuracy of conventional ultrasound remains low even after quantifying renal parenchyma echogenicity by using a software that assesses the mean pixel density [3].  
Elastography as a technique for measuring the elasticity of biological tissues was first proposed in 1991 by [PERSON] [4]. Elasticity is a feature of a tissue that allows it to deform after an initial load and then return to its original shape.  
Ultrasound elasticity imaging technology has been widely used in the differential diagnosis of benign and malignant superficial organs, such as the breast and thyroid [5], or liver fibrosis and cirrhosis [6].  
In recent years, elastography has started to be used as a non-invasive approach for the assessment of diffuse kidney disorders, the main purpose being the diagnosis and the assessment of the progression of chronic kidney disease. The importance of using this method could be the potential detection of renal damage in the early stages of chronic kidney disease when, due to the strong compensatory capacity of the kidney, the results of multiple renal indicators, such as glomerular filtration rate and urinary albumin/ creatinine ratio, can still be in the normal range if the kidney damage is not serious [7].  
Transient elastography (TE), point shear-wave elastography (p-SWE), and two-dimensional shear wave elastography (2D-SWE) are the three types of ultrasound-based elastography. Because TE is known to be inadequate for evaluating kidney stiffness (KS), published studies focused on p-SWE and 2D-SWE, both methods based on acoustic radiation force impulse (ARFI).  
In ARFI-based elastography, a transducer similar to the one integrated into an ultrasound machine is used to generate shear waves inside the organ that propagate through the soft tissue. The speed of these shear waves (SWS) is progressively reduced, and this is corresponding to tissue stiffness. The obtained result is either an average value inside a region of interest (pSWE) or a color-coded map, inside which the measurement can be performed (2D-SWE) [8].  
It is necessary to understand what influences the obtained results to establish a role for renal elastography in clinical practice. Across different studies, different factors, such as age, gender, measurement depth, and urine pressure, have been mentioned to influence the renal shear wave speed measured using different elastography methods [9]. The relationship between renal function, fibrosis, and renal stiffness assessed through different elastographic methods does not show consistency across the different studies. Not all studies showed an increase in renal stiffness in more advanced renal disease. Changes in renal blood flow appear to influence renal elastography, and a decrease in renal blood could be the reason for the decrease in shear wave speed, as well as having a greater impact on elastography than renal fibrosis [10].  
We performed a meta-analysis in order to compare different results obtained using elastography in the assessment of chronic kidney disease.