Background: CKD may be defined as either kidney damage or glomerular filtration rate <60 ml/mm/1.73 m2 for more than three months. Kidney damage is defined as pathological abnormalities or marks of damage including abnormalities in blood, urine, and imaging test. Objective: To analyze the changes in cortical thickness of the kidney and, the size of the kidney with progression to CKD. Methods: This study, conducted between May 2021 to April 2022, employed a retrospective cross-sectional design within the ultrasound department of a Tertiary Hospital. The study involved 200 CKD patients with a glomerular filtration rate (GFR) of < 60 ml/min. Serum creatinine estimation was performed alongside blood tests on the same day as ultrasonography, which assessed echogenicity, parenchymal thickness, cortical thickness, and longitudinal length. All gathered data were recorded in the pro forma. Results: The patient cohort had an average age of 54.62±13.3 years. Mean serum creatinine showed significant variance across echogenicity grades (p=0.0005). Comparable trends were observed for mean parenchymal thickness (p=0.0005), mean longitudinal length (p=0.0005), and mean corticomedullary distinction (p=0.0005). A statistically significant highly positive correlation emerged between serum creatinine and cortical echogenicity grading (r=0.915, p = 0.0005). Conclusion: Renal cortical echogenicity, particularly its grading, exhibited the most substantial correlation with serum creatinine among various sonographic parameters like longitudinal length, parenchymal thickness, and cortical thickness in CKD patients. As renal cortical echogenicity's irreversible nature contrasts with serum creatinine levels, it stands as a viable parameter for renal function assessment.