Changes in renal microcirculation in patients with nephrotic and nephritic syndrome: The role of resistive index.

BACKGROUND: Renal Resistive Index (RRI) is an important and non-invasive parameter of renal damage and it is associated with abnormal microcirculation or to a parenchymal injury. The aim of our study was to compare the RRI in a cohort of patients with renal diseases categorized in three groups: nephrotic syndrome (NS), acute nephritic syndrome (ANS) and patients with urinary abnormalities (UA). METHODS: Four hundred eighty-two patients with median age of 48 years (IQR 34-62) with indications for kidney disease were included in the study. Biochemical analyses, clinical assessment with detection of NS, ANS and UA and comorbidities were reported. Renal Doppler ultrasound with RRI was evaluated in all patients at the time of enrolment. RESULTS: NS was present in 81 (16.8 %) patients while ANS in 81 (16.8 %) and UA in 228 (47.3 %) patients. Patients with ANS showed significant higher RRI compared to both patients with NS [0.71 (IQR 0.67-0.78) vs 0.68 (0.63-0.73), p < 0.001] and UA [0.71 (0.67-0.78) vs 0.65 (0.61-0.71), p < 0.001]; RRI was higher in NS patients than in patients with UA [0.68 (0.63-0.73) vs 0.65 (0.61-0.71), p < 0.001]. Patients with ANS had significantly lower median estimated glomerular filtration rate (eGFR) compared respectively to NS and UA patients [19.7 ml/min vs 54.8 ml/min and vs 72.3 ml/min, p < 0.001], while renal length was significantly higher in patients with NS compared to both patients with ANS and UA [111.88 mm vs 101.98 mm and vs 106.15, p < 0.001]. Patients with ANS had more frequently hematuria and RRI ≥ 0.70 (p < 0.001) compared to both patients with NS and patients with UA. The multiple regression analysis, weighted for age, showed that RRI inversely correlates with eGFR (ß coefficient = -0.430, p < 0.001). CONCLUSIONS: Higher and pathological RRI were found in ANS than NS and UA. Renal resistive index in ANS reflects changes in intrarenal perfusion and microvascular dysfunction related to disease characteristics.

Doppler-Derived Intrarenal Venous Flow Mirrors Right-Sided Heart Hemodynamics in Patients With Cardiovascular Disease.

BACKGROUND: Interruption in Doppler intrarenal venous flow (IRVF) has been used in assessing renal congestion and in the prediction of prognosis of cardiovascular diseases. However, there is a paucity of pathophysiological knowledge, so we aimed to clarify the determinants of IRVF interruption.Methods and Results:Intrarenal Doppler studies were performed within 24 h before right-side catheterization studies. The interruption in IRVF in 73 patients was divided into a continuous pattern, and 4 discontinuous types based on the timing of interruption. Type 1, with an interruption in early systole, was associated with a-wave elevation of right atrial pressure (RAP). Type 2, with an interruption in early diastole, was associated with v-wave elevation, tricuspid regurgitation (TR), and right ventricular dysfunction. Both Type 1 and 2 were observed even in the normal range of mean RAP. Type 3, with an interruption throughout systole, was observed in advanced right heart failure patients with markedly elevated RAP, particularly elevated x-descend and atrial fibrillation. Finally, Type 4, with limited flow at systole, was observed in 2 of the patients with pulmonary arterial hypertension. CONCLUSIONS: IRVF interruption was closely related to RAP elevation at each specific point of the cardiac cycle rather than to mean RAP levels, suggesting that the characteristics of IRVF mirror right-sided heart hemodynamics, not mean RAP.

Late Gadolinium Enhancement in Cardiac Magnetic Resonance Imaging Is Associated with High Renal Resistive Index in Patients with Systemic Sclerosis.

INTRODUCTION: Systemic sclerosis (SSc) is a chronic autoimmune disease characterized by microvascular damage and fibrosis of the skin and internal organs. The major complications are lung fibrosis, pulmonary artery hypertension, scleroderma renal crisis, and cardiac involvement. OBJECTIVE: The aim of this study was to assess renal and cardiac involvement in asymptomatic SSc patients using renal Doppler ultrasound (RDU) and cardiac magnetic resonance (CMR). MATERIALS AND METHODS: We enrolled 26 consecutive SSc patients (21 female) according to 2013 ACR/EULAR criteria. Biochemical analysis, clinical evaluation, RDU with intrarenal hemodynamic parameters (renal resistive index [RRI], pulsatility index [PI], systolic/diastolic [S/D] ratio), and CMR with late gadolinium enhancement (LGE) were investigated at the time of enrollment. RESULTS: The median PI value was significantly (p = 0.007) higher in SSc patients with LGE than in SSc patients without LGE (1.37 [1.28-1.58] vs. 1.12 [1.06-1.26]). The median RRI value was significantly (p = 0.002) higher in SSc patients with LGE than in SSc patients without LGE (0.68 [0.65-0.73] vs. 0.64 [0.63-0.65]). The median S/D ratio was significantly (p = 0.02) higher in SSc patients with LGE than in SSc patients without LGE (3.12 [2.83-3.76] vs. 2.78 [2.64-2.84]). CONCLUSIONS: Our study, although performed on a small SSc population, showed RRI and LGE as markers of vascular and fibrotic damage. Early detection of cardiorenal involvement in SSc patients without symptoms is important to avoid further complications.

Renal Resistive Index: not only kidney.

From growing data from the literature emerges that so-called ecoDoppler "Renal" Resistive Indexes (RRI) are not only specific markers of kidney damage and indicators of renal functional prognosis but they always express more clearly a strong link with the systemic circulation. In fact, some cardiovascular parameters such as aortic pulse pressure, aortic stiffness, abdominal aortic calcifications and clinical settings for instance heart failure progression have shown a great association with RRI. Relationships between renal and inflammatory indexes in hypertensive patients have been found and data from the literature on kidney transplants underline the capability of the graft RRI to change according to host hemodynamic features. The purpose of this article is to explain the emerging pathophysiological aspects of this relationship between renal microcirculation and cardiovascular system by emphasizing the importance for the ultrasonographer and for the nephrologist of not overlooking a global vision of the patient before interpreting the RRI.

Serum uric acid as a marker of microvascular damage in systemic sclerosis patients.

BACKGROUND: Microvascular damage of skin and internal organs is a hallmark of systemic sclerosis (SSc). Serum uric acid (UA) represents a marker of inflammation and endothelial dysfunction. The aims of this study were to evaluate the correlation between serum UA and intrarenal arterial stiffness evaluated by Doppler ultrasound in SSc patients with normal renal function. We also evaluated the correlation between serum UA and other clinical variables of the disease. METHODS: Forty-five SSc patients underwent clinical assessment, Doppler ultrasound of intrarenal arteries with evaluation of resistive index (RI), pulsatile index (PI), and systolic/diastolic ratio (S/D), echocardiography with systolic pulmonary artery pressure (PAPs), baseline pulmonary function tests, and nailfold videocapillaroscopy (NVC). In all patients serum UA was measured. RESULTS: The serum UA showed a significant positive correlation with sCr (r=0.33, p<0.0001) and PAPs (r=0.38, p<0.01) >and negative correlation with CKD-EPI (r=-0.35, p<0.01). The mean value of serum UA increased with severity of NVC damage. Using this cut-off value of 4.7mg/dl, the mean value of Doppler indices of intrarenal stiffness is significantly different (p<0.05) in SSc patients with low normal or high normal serum UA. CONCLUSIONS: Serum UA concentration is higher in patients with high microvascular damage than in patients with low microvascular damage. These preliminary data must be confirmed in large prospective studies.