Clinical Research Directory

Role of Renal Duplex Resistive Index (RRI) and Pulsatility Index (PI) in Assessment of Early Renal Microvascular Changes in Diabetic Patient

Sponsor: Assiut University

Summary

Diabetes mellitus (DM) is a globally prevalent metabolic disorder with an escalating burden on renal health. Diabetic kidney disease (DKD) represents the leading cause of end-stage renal disease (ESRD) worldwide, affecting approximately 20-40% of all diabetic patients . The pathophysiology of DKD involves progressive microvascular injury characterized by glomerular hyperfiltration, mesangial expansion, tubular damage, and ultimately interstitial fibrosis, culminating in irreversible loss of renal function . Despite advances in management, a substantial subset of diabetic patients develop significant renal structural damage while remaining normoalbuminuric, rendering conventional biomarkers such as urinary albumin-to-creatinine ratio (UACR) and estimated glomerular filtration rate (eGFR) inadequate for early detection . Conventional renal screening relies heavily on serum creatinine and albuminuria thresholds; however, these markers reflect filtration loss that occurs only after considerable parenchymal injury has already taken place . Novel tubular biomarkers such as neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1) have shown promise in detecting early tubular damage, yet their routine clinical applicability remains limited by cost and lack of standardized thresholds . Renal biopsy, the gold standard for histological staging of DKD, is invasive, carries hemorrhagic risk, and is entirely impractical as a population-level screening tool . Renal Duplex Doppler ultrasonography has emerged as a valuable, safe, non-invasive modality for assessing intrarenal hemodynamics. The Renal Resistive Index (RRI), calculated as (Peak Systolic Velocity - End Diastolic Velocity) / Peak Systolic Velocity, and the Pulsatility Index (PI), defined as (Peak Systolic Velocity - End Diastolic Velocity) / Mean Velocity, reflect downstream microvascular impedance and arteriolosclerosis . Elevated RRI values have been independently associated with progressive renal functional decline, systemic arterial stiffness, and adverse cardiovascular outcomes across multiple patient populations . In the context of Type 2 Diabetes Mellitus (T2DM), elevated RRI has been consistently demonstrated to correlate with disease duration, poor glycemic control, microalbuminuria, and declining eGFR, with a diagnostic cut-off of approximately 0.65-0.70 proposed in several studies . Mahmoud et al. (2023) demonstrated that diabetic patients exhibited significantly higher mean RRI values compared to healthy controls, underscoring the utility of intrarenal Doppler indices in detecting early nephropathy before overt albuminuria manifests . In Type 1 Diabetes Mellitus (T1DM), particularly in pediatric and young adult cohorts, RRI has been shown to rise in parallel with glycemic variability and tubular injury markers, preceding the onset of microalbuminuria by years . The relationship between RRI and systemic microvascular complications such as retinopathy and neuropathy has also been explored, with evidence suggesting that elevated RRI may serve as a surrogate marker of global microvascular disease burden in diabetic patients . Furthermore, dynamic RRI assessment following physiological stimulation has demonstrated predictive value for long-term renal outcome in both T2DM and hypertensive patients . The prognostic significance of RRI extends beyond renal function, with studies reporting its independent association with major adverse cardiovascular events and all-cause mortality in chronic kidney disease populations . Despite this accumulating evidence, a critical gap remains: the vast majority of published studies have examined T1DM and T2DM populations independently, under heterogeneous Doppler acquisition protocols and with varying patient selection criteria. No adequately powered, three-arm comparative study has simultaneously evaluated RRI and PI across T1DM, T2DM, and matched healthy controls under a single, rigorously standardized protocol. Furthermore, data specific to the Egyptian population, which carries one of the highest global burdens of adult diabetes and diabetic nephropathy, are remarkably scarce. This study is therefore designed to address this methodological gap by conducting a structured comparative cross-sectional analysis of RRI and PI across all three groups, with comprehensive correlation to clinical, glycemic, and renal parameters, to establish locally validated diagnostic thresholds and advance the role of renal duplex sonography as a frontline early screening tool for diabetic renal microvascular disease.

Official title: Role of Renal Duplex Resistive Index in the Assessment of Early Renal Microvascular Changes in Type 1 and Type 2 Diabetes Mellitus: A Comparative Study of the Renal Resistive Index (RRI) and Pulsatility Index (PI) Among Type 1 Diabetic, Type 2 Diabetic, and Non-Diabetic Subjects

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