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.

Assessment of renal microcirculation in biopsy-proven tubulointerstitial nephritis in patients with and without glomerular disease: the role of resistive index.

BACKGROUND: Renal resistive index (RRI) measured by Doppler sonography is a marker of microvascular status and it is associated with changes in renal function. Aim of the study was to assess RRI in biopsy-proven tubulointerstitial nephritis (TIN) in patients with and without glomerular disease. METHODS: 132 consecutive patients underwent to native renal biopsy with diagnosis of isolated TIN or in association with glomerulonephritis. Estimated glomerular filtration rate (eGFR), 24-hour urinary protein excretion and renal ecocolorDoppler ultrasonography with RRI assessment were performed at time of enrollment. RESULTS: Patients with isolated-TIN had significantly higher RRI than both patients with non-immunoglobulin A glomerulonephritis (non-IgA-TIN) [0.73 (0.68-0.77) vs 0.64 (0.60-0.67), p < 0.001] and patients with IgA nephropathy (IgAN) [0.73 (0.68-0.77) vs 0.66 (0.60-0.71), p < 0.01]. Patients with isolated-TIN had mainly RRI ≥ 0.70 (n = 15, 65.2%) with the respect to patients with non-IgA-TIN (n = 7, 12.3%) and patients with IgAN (n = 17, 32.7%). A negative linear correlation was found between RRI and hemoglobin (r = 0.233, p < 0.01) and between RRI and eGFR (r = 0.537, p < 0.001). CONCLUSION: Tubulointerstitial damage is the most accurate histological lesion that correlates with eGFR and renal impairment. RRI can be a useful parameter to detect tubulointerstitial lesions.