Study of Cystatin C and Renal Resistive Index in Type 2 Diabetes Mellitus Patients to Detect Early Diabetic Kidney Disease

Background: Diabetic kidney disease (DKD) is a major cause of chronic kidney disease and end-stage renal failure among individuals with type 2 diabetes mellitus (T2DM). Traditional markers such as serum creatinine and albuminuria have limited sensitivity in early disease stages. Cystatin C and renal resistive index (RRI) are emerging as sensitive early indicators. Objectives: The study aimed to assess the diagnostic utility of serum cystatin C and RRI in the early detection of renal dysfunction in T2DM patients and to evaluate their correlation with estimated glomerular filtration rate (eGFR) and urinary albumin-to-creatinine ratio (UACR). Materials and Methods: A cross-sectional study involving 100 patients with T2DM was conducted. Serum cystatin C, serum creatinine, urine albumin, and eGFR (using Chronic Kidney Disease Epidemiology Collaboration creatinine–cystatin equation) were measured. Doppler ultrasonography was used to determine RRI. Pearson’s correlation and multiple regression analyses were performed. Results: Elevated cystatin C levels were seen in 91% of subjects, whereas only 63% had abnormal serum creatinine. RRI was raised in 62% of patients. eGFR correlated negatively with UACR ( r = −0.998), serum creatinine ( r = −0.881), RRI ( r = −0.712), and cystatin C ( r = −0.552). UACR and RRI were significant predictors of eGFR in multivariate analysis ( P < 0.001 and P = 0.030, respectively). Conclusion: Cystatin C and RRI provide early insights into renal dysfunction in T2DM and should be integrated with existing diagnostic parameters for improved DKD screening.