## 1 Introduction  
According to an estimate by the U.S. Centers for Disease Control and Prevention (CDC) in 2021, 37 million adults in the United States suffer from chronic kidney disease (CKD) [1]. In addition to blood and urine tests, ultrasound is the most commonly used imaging diagnostic tool by nephologists for the early detection of chronic kidney disease. Ultrasonography is a suitable approach for diagnosing kidney disease because the renal cortex and medulla tissues possess different densities and hence the difference between the tissues can be easily observed [2]. Though magnetic resonance angiography (MRA) and computed tomography angiography (CTA) can display clearer vascular images with higher resolution than ultrasonography, and advanced machines can even provide 3D images directly. However, compared with MRA and CTA medical imaging, ultrasonography has the advantages of non-ionizing radiation, is non-invasive, safe, portable, inexpensive, and can be easily operated by medical staff [3, 4]. Therefore, ultrasonography has become the most commonly used and indispensable imaging tool in nephrology. With the increasing popularity of inexpensive portable ultrasound scanners coupled with professional training guidelines for renal ultrasonography, nephrologists can operate ultrasound imaging equipment and easily interpret the diagnosed results [5]. Ultrasonography can currently assist nephrologists in the diagnosis of all aspects of nephrology,including acute and chronic renal failure, renal blood vessels, kidney stones, tumors, infections, renal trauma, and guiding percutaneous biopsy, etc. [6]. This non-invasive diagnosis approach is a low-cost and safe investigation suitable for outpatient visits and can be used as the first-line investigation for the preliminary diagnosis of kidney diseases [4]. However, the presence of speckle noise in ultrasound images degrades the image quality. Interpretation of renal sonograms is highly dependent on the experience of nephrologists in correctly diagnosing a patient's condition. While making a CKD diagnosis, different nephrologists may have different interpretations of CKD stages from an identical ultrasound image or even the same nephrologist may have inconsistent interpretation at different times [7]. Ultrasonography is an important investigation for patients with chronic kidney disease. Nephrologists can evaluate kidney function based on measuring length, volume, cortical thickness, and cortical echogenicity of the kidney through a sonogram, and make a final decision on whether to proceed with a kidney biopsy or not [5,6]. Multiple studies have found that kidney length and partial renal cortical echogenicity are significantly correlated with overall sclerosis, focal tubular atrophy, and the number of glomeruli [8,9]. According to a study by [PERSON] et al., 67% of patients with renal parenchymal diseases can be diagnosed with corresponding abnormalities using ultrasonography [10]. According to a research report by [PERSON] et al., the highest echo intensity of renal cortical echogenicity is 62% higher than that of a normal kidney, which is several times larger than the margin of error of ultrasonic instruments [11]. [PERSON] et al. measured the length and volume of the kidneys using magnetic resonance imaging (MRI). The length of male and female kidneys was 12.4 \(\pm\) 0.9 cm and 11.6 \(\pm\) 1.1 cm, respectively, while the volume of male and female kidneys was 202 \(\pm\) 36 mL, and 154 \(\pm\) 33 mL, respectively [12]. The study by [PERSON] et al. showed that with the progression of renal failure, the length and volume of renal parenchyma were significantly reduced in patients with CKD from stage 1 to stage 3. For patients at stages 4 to 5, the volume of the kidney parenchyma was significantly reduced [13]. According to [PERSON] et al. and [PERSON] et al., the correlation coefficients of kidney length and Estimated Glomerular Filtration Rate (eGFR) were only 0.34 and 0.36, respectively [14,15]. However, [PERSON] et al.