Comparison of renal resistive index among patients with Type 2 diabetes with different levels of creatinine clearance and urinary albumin excretion

Cardiovascular risk and renal injury profile in subjects with type 2 diabetes and non-albuminuric diabetic kidney disease

BACKGROUND

In the last years, the classical pattern of diabetic kidney disease (DKD) has been partially overcome, because of the uncovering of a new DKD phenotype with significant renal dysfunction without presence of albuminuria: the non-albuminuric DKD (NA-DKD). To date, the cardiovascular risk associated with this phenotype is still debated. We investigated the cardiovascular risk and renal injury profile of NA-DKD subjects in comparison with other DKD phenotypes.

METHODS

Pulse wave velocity (PWV), intima-media thickness, presence of carotid atherosclerotic plaque, renal resistive index (RRI), and a panel of urinary biomarkers of kidney injury were evaluated in 160 subjects with type 2 diabetes, stratified according to estimated glomerular filtration rate (eGFR) and urinary albumin to creatinine ratio (UACR) into four groups: controls (UACR < 30 mg/g and eGFR ≥ 60 mL/min/1.73 m2), A-DKD (Albuminuric-DKD, UACR ≥ 30 mg/g and eGFR ≥ 60 mL/min/1.73 m2), NA-DKD (UACR < 30 mg/g and eGFR < 60 mL/min/1.73 m2), AL-DKD (Albuminuric and Low eGFR-DKD; UACR ≥ 30 mg/g and eGFR < 60 mL/min/1.73 m2).

RESULTS

Subjects with NA-DKD showed a higher PWV (11.83 ± 3.74 m/s vs. 10.24 ± 2.67 m/s, P = 0.045), RRI (0.76 ± 0.11 vs. 0.71 ± 0.09, P = 0.04), and prevalence of carotid atherosclerotic plaque (59% vs. 31%, P = 0.009) compared with controls. These characteristics were similar to those of subjects with AL-DKD, whereas the profile of A-DKD subjects was closer to controls. After multiple regression analyses, we found that RRI, that is in turn influenced by eGFR (β = - 0.01, P = 0.01), was one of the major determinants of PWV (β = 9.4, P = 0.02). Urinary TreFoil Factor 3, a marker of tubular damage, was higher in NA-DKD subjects vs. controls (1533.14 ± 878.31 ng/mL vs. 1253.84 ± 682.17 ng/mL, P = 0.047). Furthermore, after multiple regression analyses, we found that urinary osteopontin was independently associated with PWV (β = 2.6, P = 0.049) and RRI (β = 0.09, P = 0.006).

CONCLUSIONS

Our data showed a worse cardiovascular and renal injury profile in NA-DKD subjects. This finding emphasizes the central role of eGFR in the definition of cardiovascular risk profile of diabetic subjects together with albuminuria.

Prognostic significance of the renal resistive index in the primary prevention of type II diabetes

The renal resistive index has been demonstrated to predict the progression of renal disease and recurrence of major cardiac events in high-risk cardiovascular patients, in addition to other comorbidities. We aimed to assess the prognostic significance of the renal resistive index in type 2 diabetic patients for primary prevention. From 2008 to 2011, patients with type 2 diabetes underwent cardiovascular evaluation, including renal resistive index assessment by renal Doppler ultrasound. The incidence of all-cause death, cardiovascular events, dialysis requirement or a twofold increase in creatinine was recorded. Survival curves were estimated by the Kaplan-Meier method. Two hundred sixty-six patients were included; 50% of the patients were men, an HbA1C level of 8.1 ± 1.7% (65 ± 13.6 mmol/mol) and a serum creatinine level of 8 [7-9] mg/L. The mean 24-hour systolic blood pressure, 24-hour diastolic blood pressure, and 24-hour pulse pressure were 133.4 ± 16.7, 76.5 ± 9.4, and 56.9 ± 12.4 mm Hg, respectively. The median renal resistive index was 0.7 [0.6-0.7] with a threshold of 0.7 predictive of monitored events. After adjustment of the 24-hour pulse pressure, age and 24-hour heart rate, a renal resistive index ≥0.70 remained associated with all-cause death (hazard ratio: 3.23 (1.16-8.98); P = .025) and the composite endpoint of major clinical events (hazard ratio: 2.37 (1.34-4.18); P = .003). An elevated renal resistive index with a threshold of 0.7 is an independent predictor of a first cardiovascular or renal event in type 2 diabetic patients. This simple index should be implemented in the multiparametric staging of diabetes.

Renal intraparenchymal resistive index: the ultrasonographic answer to many clinical questions

The use of renal resistive indices (RRIs) for the study of renal microcirculation has in the past been proposed for the identification of renal organ damage or even to specifically identify injury to some areas of the renal parenchyma. Nevertheless, according to the most recent evidences from literature this organ-based conception of RRIs has been proven to be partial and unable to explain the RRIs variations in clinical settings of sepsis or combined organ failure of primitively extrarenal origin or, more generally, the deep connection between RRIs and hemodynamic factors such as compliance and pulsatility of the large vessels. The aim of this review is to explain the physiopathological basis of RRIs determination and the most common interpretative errors in their analysis. Moreover, through a comprehensive vision of these Doppler indices, the traditional and emerging clinical application fields for RRIs are discussed.

Increased renal resistive index in type 2 diabetes: Clinical relevance, mechanisms and future directions

Type 2 diabetes is a global health challenge. In type 2 diabetes both microvascular (nephropathy, retinopathy, neuropathy) and macrovascular complications arise. In 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 arterioles. Renal resistive index (RRI) is defined as a ratio of the difference between maximum and minimum (end-diastolic) flow velocity to maximum flow velocity derived from the Doppler measurements of main renal and intrarenal (segmental/interlobar) arteries. Renal resistive index is tightly related to renal arteriolosclerosis, and represents an integrated index of arterial compliance, pulsatility and downstream microvascular impedance. In meantime, growing suggest that RRI has also been closely related with atherosclerosis. Most studies performed in type 2 diabetes showed RRI is increased in type 2 diabetes. In this review, we summarize the data regarding RRI with regard to performed studies, pathogenesis and prognosis, especially focusing on type 2 diabetes (T2D). We also review the data regarding the development of metabolic syndrome (MetS) and RRI.

PARP inhibition ameliorates nephropathy in an animal model of type 2 diabetes: focus on oxidative stress, inflammation, and fibrosis

Poly(ADP-ribose) polymerase (PARP) enzyme contributes to nephropathy, a serious diabetic complication which may lead to end-stage renal disease. The study aims to investigate the effect of PARP over-activation on kidney functions in a type 2 diabetic rat model. The study also tests the therapeutic use of PARP inhibitors in diabetic nephropathy. Type 2 diabetes was induced in adult male rats by high-fructose/high-fat diet and low streptozotocin dose. Then, the PARP inhibitor 4-aminobenzamide (4-AB) was administered daily for 10 weeks. At the end, urine samples were collected to measure urine creatinine, albumin, and total proteins. PARP activity, superoxide dismutase (SOD) activity, and nitrite content were measured in kidney tissue homogenate. Glucose, fructosamine, insulin, and tumor necrosis factor-alpha (TNF-α) were measured in serum. Furthermore, histological studies, collagen deposition, and immunofluorescence of nuclear factor kappa B (NFκB) and transforming growth factor beta1 (TGF-β1) were carried out. PARP enzyme activity was significantly higher in the diabetic group and was significantly reduced by 4-AB administration. Diabetic animals had clear nephropathy indicated by proteinuria and increased albumin excretion rate (AER) which were significantly decreased by PARP inhibition. In addition, PARP inhibition increased creatinine clearance in diabetic animals and reduced renal TGF-β1 and glomerular fibrosis. Moreover, PARP inhibition alleviated the elevated serum TNF-α level, renal NFκB, nitrite, and the decrease in SOD activity in diabetic animals. However, PARP inhibition did not significantly affect neither hyperglycemia nor insulin sensitivity. PARP enzyme inhibition alleviates diabetic nephropathy through decreasing inflammation, oxidative stress, and renal fibrosis.

The evaluation of renal hemodynamics changes in Familial Mediterranean fever with color Doppler sonography

BACKGROUND

Renal resistive index (RRI) scanned through renal Doppler is a practical marker employed in measuring blood flow in renal and intrarenal arteries and in noninvasive evaluation of renal vascular resistance. We aimed to investigate the renal hemodynamic variations in patients with Familial Mediterranean Fever (FMF).

MATERIAL AND METHODS

Seventy-nine FMF patients and 51 healthy subjects suitable for age and sex were included. Patients were divided into two groups according to their urinary albumin excretion. Fifty-two patients with 0-29 mg/day albuminuria were included in the normoalbuminuric group while 27 patients with 30-299 mg/day albuminuria were included in the microalbuminuric group.

RESULTS

RRI values were higher in patients with FMF compared to the healthy subjects (p < 0.0001). Additionally, RRI values were found to be higher in the microalbuminuric patients group compared to the normoalbuminuric patients group, and RRI values were also higher in normoalbuminuric patients group compared to the control group (p = 0.002, p < 0.0001). The ROC curve analysis suggested that the optimum RRI cutoff value for microalbuminuria in patients was 0.63, sensitivity of 66%, specificity of 60%, and p = 0.013.

CONCLUSION

RRI may be a marker that may be used in assessing resistance to renal blood flow, early renal damage, and progression of renal damage in FMF patients.

MMP-9- and NMDA receptor-mediated mechanism of diabetic renovascular remodeling and kidney dysfunction: hydrogen sulfide is a key modulator

Previously we reported that matrix metalloproteinase-9 (MMP-9) plays an important role in extracellular matrix (ECM) remodeling in diabetic kidney. Induction of NMDA-R and dysregulation of connexins (Cxs) were also observed. We concluded that this was due to decreased H2S production by downregulation of CBS and CSE enzymes. However, the potential role of H2S to mitigate ECM dysregulation and renal dysfunction was not clearly understood. The present study was undertaken to determine whether H2S supplementation reduces MMP-9-induced ECM remodeling and dysfunction in diabetic kidney. Wild type (C57BL/6J), diabetic (Akita, C57BL/6J-Ins2(Akita)), MMP-9 knockout (MMP-9(-/-), M9KO) and double KO of Akita/MMP-9(-/-) (DKO) mice were treated without or with 0.005 g/l of NaHS (as a source of H2S) in drinking water for 30 days. Decreased tissue production and plasma content of H2S in Akita mice were ameliorated with H2S supplementation. Dysregulated expression of MMP-9, CBS, CSE, NMDA-R1 and Cxs-40, -43 was also normalized in Akita mice treated with H2S. In addition, increased renovascular resistive index (RI), ECM deposition, plasma creatinine, and diminished renal vascular density and cortical blood flow in Akita mice were normalized with H2S treatment. We conclude that diminished H2S production in renal tissue and plasma levels in diabetes mediates adverse renal remodeling, and H2S therapy improves renal function through MMP-9- and NMDA-R1-mediated pathway.

Duplex scanning has a limited role in the evaluation of patients with renal failure

OBJECTIVE

Although common indications for renal duplex scanning (RDS) include hypertension (HT) and renal failure (RF), the role of RDS in the evaluation of patients with RF is not known. The goal of this study was to define ultrasound findings with predictive or discriminatory value in patients with RF and to identify patients undergoing a renal artery intervention as a result of RDS findings.

METHODS

We conducted a retrospective review of 214 consecutive patients referred to an Intersocietal Accreditation Commission-accredited vascular laboratory for an initial RDS from January 1, 2010, to June 30, 2010. RDS included direct ultrasound evaluation of the main renal vessels and renal parenchyma. Significant renal artery stenosis of ≥ 60% diameter reduction was indicated by a renal/aortic velocity ratio ≥ 3.5 and abnormally increased parenchymal resistance by an end-diastolic ratio ≤ 0.3.

RESULTS

We separated the patients into two groups by indication for RDS: Group I (HT alone, n = 102) and group II (RF alone or with HT, n = 112). When group I was compared with group II, there were significant differences in gender (50% vs 67% male; P = .013), age (50.9 ± 18.5 vs 60.0 ± 14.8 years; P < .001), mean arterial pressure (103.1 ± 18.8 vs 85.7 ± 17.0 mm Hg; P < .001), and creatinine (0.95 ± 0.35 vs 2.25 ± 1.07 mg/dL; P < .001). In group I patients, 86 (84.3%) had normal parenchymal resistance, whereas in group II patients, 68 (60.7%) had abnormally increased parenchymal resistance unilaterally or bilaterally (P < .001). Unilateral or bilateral renal artery stenosis was identified in six group I patients and in three group II patients (P = .315). Evaluation of group II patients revealed a diagnosis of decompensated congestive heart failure (CHF) and the presence of unilateral or bilateral increased parenchymal resistance in 27 of 68 (39.7%) vs nine of 44 (20.4%) with CHF and normal parenchymal resistance. One renal artery angioplasty was performed in a patient with unilateral renal artery stenosis and fibromuscular dysplasia.

CONCLUSIONS

Renal artery stenosis is extremely uncommon in patients undergoing RDS for RF, indicating that ischemic nephropathy is rarely a cause of RF in these patients. Abnormally increased renal parenchymal resistance is frequently found in patients being evaluated for RF and is associated with increasing creatinine and age. A diagnosis of CHF is also more common in patients with increased parenchymal resistance. Although patients who undergo RDS for RF rarely require renal artery interventions, ultrasound indices of parenchymal resistance may serve as a marker for renal disease and cardiovascular morbidity. Further studies are required to determine the prognostic significance of these ultrasound findings in the setting of RF.

Resistive intrarenal index: myth or reality?

In renal diagnosis, the B-mode ultrasound is used to provide an accurate study of the renal morphology, whereas the colour and power Doppler are of strategic importance in providing qualitative and quantitative information about the renal vasculature, which can also be obtained through the assessment of the resistive index (RI). To date, this is one of the most sensitive parameters in the study of kidney diseases and allows us to quantify the changes in renal plasma flow. If a proper Doppler ultrasound examination is carried out and a critical analysis of the values obtained is performed, the RI measurement at the interlobar artery level has been suggested in the differential diagnosis between nephropathies. The aim of this review is to highlight the pathological conditions in which the study of intrarenal RI provides useful information about the pathophysiology of renal diseases in both the native and the transplanted kidneys.