Beyond eGFR and proteinuria: Noninvasive ultrasonographic markers of renal impairment in diabetic kidney disease

Abstract

Current literature regarding the combined associations of structural renal ultrasonographic parameters and renal resistive index (RRI) with diabetic kidney disease (DKD) severity remains limited, particularly in Southeast Asian populations. The aim of this study was to explore the associations of renal ultrasonographic parameters with estimated glomerular filtration rate (eGFR) and proteinuria among patients with DKD. A cross-sectional study was conducted involving 51 patients with DKD. Bilateral renal longitudinal diameter, cortical thickness, parenchymal echogenicity, and RRI were assessed using ultrasonography. Renal function was evaluated using the 2021 Chronic Kidney Disease Epidemiology Collaboration creatinine-based eGFR equation, and proteinuria was categorized from urine dipstick results as absent-to-mild (negative, trace, or 1+) or moderate-to-severe (2+ to 4+). The present study found that higher eGFR correlated with greater right renal longitudinal diameter (r=0.347, p=0.013), but not with left renal diameter (r=0.253, p=0.073). Cortical thickness was not correlated with eGFR in either kidney. RRI was inversely correlated with eGFR bilaterally (r=−0.491 for both; p<0.001). Mean eGFR was numerically lower in patients with increased parenchymal echogenicity than in those with normal echogenicity, but the differences were not significant. Renal longitudinal diameter, cortical thickness, and parenchymal echogenicity did not differ significantly between proteinuria groups. The mean right RRI was lower in patients with moderate-to-severe proteinuria than in those with absent-to-mild proteinuria (0.66±0.11 vs 0.75±0.08, p=0.038), whereas left RRI did not differ significantly (p=0.231). In conclusion, bilateral RRI was consistently associated with lower eGFR, whereas associations involving structural ultrasonographic parameters and proteinuria were less consistent, suggesting that RRI may complement conventional assessment of kidney function in DKD; however, its clinical and prognostic value requires confirmation in larger prospective studies.