Renal Resisitive Index as an Indicator of the Progression of Diabetic Nephropathy

Overview

diabetic nephropathy is one of the leading causes of end stage renal disease

Diabetes mellitus is one of the systemic diseases affecting the kidneys. Diabetic nephropathy is a serious microvascular complication of diabetes mellitus. It is the most important cause of death in type I diabetic patients, of whom 30%-40% eventually develop end-stage renal failure and 40% of type II diabetics are at risk of developing diabetic nephropathy. So, diagnosis of diabetic nephropathy is paramount for the survivability of the diabetic patients not only because of the consequences of renal progression but also because of the strong association with the risk of developing cardiovascular disease Diabetic nephropathy (DN) is defined as persistent proteinuria greater than 500 mg/24 h, or albuminuria greater than 300 mg/24 h. In the kidney, renal pathological changes leading to diabetic nephropathy are mainly secondary to atherosclerosis of the intra and extra renal arteries together with microangiopathy of the glomerular capillaries, afferent arterioles and efferent arteriole. Doppler sonography may be a useful complementary test in the evaluation of DN, even in the early stages. Early stage of vascular involvement seems, in fact, to be characterized by functional alterations of endothelial control on vascular tone and wall interaction with circulating cells. Renal Doppler assessment of RI is a reliable, non-invasive evaluation of arterial function and is particularly useful for early diagnosis of vascular involvement. Increasing evidence suggests that the intra-renal arterial RI, measured by Doppler ultrasound, a well-established technique for the investigation of renal morphology and hemodynamics, predicts the course of renal function in several conditions. No standard, validated, cut-off to distinguish normal from high RI has been identified to date. RI values between 0.75 and 0.85 have been associated with renal functional impairment in patients with chronic kidney disease and stenosis of the renal artery, and they also predict allograft dysfunction in kidney transplant recipients Little information is available on the use of RI for the identification and prediction of DN in routine clinical practice. It is yet unclear whether RI predicts DN in low-risk patients; also, the correlation between increased intra-renal RI and altered renal hemodynamics remains unclear independent of albuminuria, as also the most appropriate cut-off value The renal arterial resistive index (RI) is a sonographic index to assess for renal arterial disease. It is measured as RI = (peak systolic velocity - end diastolic velocity ) / peak systolic velocity Measured at arcuate arteries (at the corticomedullary junction) or interlobar arteries (adjacent to medullary pyramids) intrarenal resistive index (RI) has been reported to be increased in hypertensive subjects with microalbuminuria and limited data is present for diabetic subjects.

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