Intrarenal Arterial Resistive Index Research Articles

A Correlation Between Direct and Indirect Doppler Ultrasonographic Measures in Transplant Renal Artery Stenosis

Screening for transplant renal artery stenosis (TRAS) with Doppler ultrasonography (DUS) is increasingly used in the era of kidney transplantation. Direct Doppler study of the stenotic site is a time- consuming and difficult method that requires an angle of interrogation parallel to the vessel. The aim of this study was to assess the correlation between the direct—PSVs (peak systolic velocity at the stenotic site), PSVs/PSVi (PSVi, peak systolic velocity of the adjacent iliac artery)—and indirect—intrarenal arterial resistive index (RI), perfusion index (PI), acceleration time (AT)—DUS findings in the kidney transplant recipients with TRAS. We performed 26 DUS studies of both intrarenal and main renal arteries in 19 TRAS patients (who had PSVs > 150 cm/s, PSVs/PSVi > 2). The mean values of PSVs and PSVs/PSVi were 212 ± 44.19 cm/s and 2.77 ± 0.77, respectively. The mean intrarenal RI, PI, and AT were 0.48 ± 0.065, 0.70 ± 0.12, and 177.8 ± 54.6 msec, respectively. A significant negative correlation was found between PSVs and intrarenal RI (Pearson correlation coefficient ( r) = −0.4, two-tailed P = .043). No correlation was found between intrarenal PI or AT and the direct DUS findings ( P > .05). With a cutoff level of 0.55 for intrarenal resistive index, the sensitivity of this parameter to detect proximal renal arterial stenosis was about 85%. Conclusively, PSVs and intrarenal RI were negatively correlated. Intrarenal resistive index can be used as an screening measure for detection of TRAS.

Early assessment of renal resistance index after kidney transplant can help predict long-term renal function

Color Doppler ultrasonography of intrarenal arterial resistance index (RI), performed early after kidney transplant, has proven to reliably predict short-term allograft function. The aim of this study was to assess whether it could also predict long-term renal function. We retrospectively analysed 76 kidney transplant patients who underwent RI assessment within 1 month after the transplant, subdivided into two groups according to RI values, lower (group A) or higher (group B) than its median value (0.635). Compared with group A subjects, the patients of group B were older at the time of transplant (42 +/- 9 vs 35 +/- 8 years; P = 0.001), the donor age was also older (41 +/- 16 vs 33 +/- 13 years; P = 0.02) and had a slightly higher proteinuria (0.54 +/- 0.5 vs 0.32 +/- 0.2 g/24 h; P = 0.02). Serum creatinine, ciclosporin or tacrolimus trough level, arterial blood pressure, number of human leukocyte antigen (HLA) mismatches, anti-hypertensive medications and incidence of delayed graft function were not significantly different between the two groups. By univariate analysis, RI turned out to directly correlate with the recipient age, donor age and daily proteinuria (P = 0.007, P = 0.0007 and P = 0.02, respectively). Multivariate analysis showed that only donor and recipient age maintained their independent predictive value on RI. Kaplan-Meier analysis, considering a serum creatinine increase >50% as the endpoint of the study, showed a statistically significant different graft survival in the two groups (log-rank test = 5.489; P = 0.01). The univariate relative risk of deterioration of graft function among patients with higher RI was 3.77. Proteinuria and recipient age increased the risk as well. Our data seem to suggest that early determination of RI can help predict long-term graft function in kidney transplant recipients.

Is Nonalbuminuric Renal Insufficiency in Type 2 Diabetes Related to an Increase in Intrarenal Vascular Disease?

To investigate the role of intrarenal vascular disease in the pathogenesis of nonalbuminuric renal insufficiency in type 2 diabetes. We studied 325 unselected clinic patients who had sufficient clinical and biochemical information to calculate an estimated glomerular filtration rate (eGFR) using the Modified Diet in Renal Disease six-variable formula, at least two estimations of urinary albumin excretion rates (AER), and a renal duplex scan to estimate the resistance index of the interlobar renal arteries. The resistance index, measured as part of a complications surveillance program, was compared in patients with an eGFR < or >or=60 ml/min per 1.73 m(2) who were further stratified into normo- (AER <20), micro- (20-200), or macroalbuminuria (> 200 microg/min) categories. Patients with an eGFR <60 ml/min per 1.73 m(2) had a higher resistance index of the renal interlobar arteries compared with patients with an eGFR >or=60 ml/min per 1.73 m(2). However, the resistance index was elevated to a similar extent in patients with an eGFR <60 ml/min per 1.73 m(2) regardless of albuminuric status (normo- 0.74 +/- 0.01, micro- 0.73 +/- 0.01, and macroalbuminuria resistance index 0.75 +/- 0.11). Multiple regression analysis revealed that increased age (P < 0.0001), elevated BMI (P = 0.0001), decreased eGFR (P < 0.01), and decreased diastolic blood pressure (P < 0.01), but not an increased AER, were independently associated with an elevated resistance index in patients with impaired renal function. Subjects with type 2 diabetes and reduced glomerular filtration rate had similar degrees of intrarenal vascular disease, as measured by the intrarenal arterial resistance index, regardless of their AER status. The pathological mechanisms that determine the relationship between impaired renal function and AER status in subjects with type 2 diabetes remain to be elucidated.

Influence of age on intrarenal resistive index measurement in normal subjects.

We investigated the influence of age on intrarenal arterial resistive index (RI) measurement in 135 normal subjects (71 male, 64 female; age range = 17-68 years, median age = 37 years). Each subject underwent color Doppler measurement of the intrarenal RI from three distinct interlobar arteries in the superior, middle, and inferior parts of both kidneys. The mean of six RI values obtained from both kidneys was used for analysis. The correlation of RI with different variables was investigated by linear regression and stepwise multiple linear regression. Variables analyzed were age, systolic blood pressure, diastolic blood pressure, mean blood pressure, pulse pressure, and pulse rate. The results of linear regression showed that age had a significantly positive correlation ( r = 0.276, p = 0.0012) and diastolic blood pressure had a significantly negative correlation ( r = -0.186, p = 0.0311) with the RI. The results of stepwise multiple linear regression showed that the combination of age and diastolic blood pressure could explain approximately 15% of the RI changes ( r(2) = 0.1535). Although there is a statistically significant positive correlation between intrarenal RI and age, the correlation is weak. This suggests that the influence of age on RI measurement is small and may be of no clinical importance.

Influence of posture change on intrarenal arterial resistive index measurement.

We investigated the influence of posture change on intrarenal arterial resistive index measurement in 80 subjects (38 male, 42 female). Three interlobar arteries in the superior, middle, and inferior parts of the right kidney in each subject were examined by color Doppler ultrasound in two different positions (left lateral decubitus and supine). Based on the movement of the kidney caused by posture change, 23 subjects were classified as having a highly mobile kidney (group I) and the other 57 subjects were classified as not having a highly mobile kidney (group II). Fifty-eight kidneys (72.5%), 19 in group I (82.6%) and 39 in group II (68.4%), showed higher resistive index values in the lateral decubitus position than in the supine position. The influence of posture change on resistive index measurement was significant ( p < 0.001 for all subjects, p < 0.01 for group I, p < 0.05 for group II). The ranges of resistive index differences caused by posture change were 0-0.13 for group I and 0-0.11 for group II. The difference in resistive index caused by posture change was not significant between groups. Posture change is a potential confounding factor for intrarenal resistive index measurement.

Ecotomografía Doppler arterial intrarrenal en pacientes cirróticos con ascitis, con y sin síndrome hepatorrenal

The pathophysiological hallmark of the hepatorenal syndrome (HRS) is renal vasoconstriction. Doppler ultrasonography can be used to assess the vascular resistance in small renal intraparenchymal vessels through analysis of the Doppler waveform by a parameter termed Resistive Index (RI). We postulated that the RI could be important for the diagnosis and prognosis of HRS. To assess the RI in cirrhotic patients with ascites, with and without HRS. We studied 48 cirrhotics with ascites, of whom 12 were with and 36 without HRS and other 23 were normal subjects. We measured the intrarenal arterial RI (Resistive index = Peak systolic velocity - Minimum diastolic velocity/Peak systolic velocity) with color Doppler ultrasonography after visualization of interlobular or arcuate arteries. It was considered abnormal when higher than 0.70. The RI values, mean and SD) were: normal subjects: 0.58 +/- 0.05, cirrhotics with ascites: 0.65 +/- 0.05 and cirrhotics with ascites and HRS: 0.78 +/- 0.11. Patients with HRS had significantly higher values than those without HRS (p < 0.001). The Relative Risk of developing the HRS in patients with a RI > or = 0.70 were 3.32 (CI 95% = 1.79-6.2) The RI was useful in patients with cirrhosis and ascites for the prognosis of HRS and could suggest diagnosis of HRS with values of 0.78 or higher, if other clinical conditions that produce renal vasoconstriction are excluded.

Renal hemodynamic changes in children with liver cirrhosis.

To assess the sensitivity of duplex Doppler ultrasonography in detecting early impairment of renal function in childhood cirrhosis, intrarenal arterial pulsatility index (PI) and resistive index (RI) were measured in 10 ascitic and 11 non-ascitic children with liver cirrhosis and normal creatinine clearance and 10 age- and sex-matched controls. PI and RI were higher in ascitic than non-ascitic children [PI 1.54+/-0.4 vs. 1.1+/-0.2 (mean +/- SD), P=0. 006; RI 0.76+/-0.07 vs. 0.68+/-0.07, P=0.03). Non-ascitic patients had higher PI and RI than controls (P=0.002 and 0.0001, respectively). PI was inversely correlated with creatinine clearance (r=-0.54, P=0.01). A significant positive relationship was observed between both PI and RI and Child score (r=0.47, P=0.009; r=0.45, P=0. 01, respectively). However, no significant correlation was observed between PI and RI and portal hypertension. We conclude that renal vascular resistance indexes evaluated by duplex Doppler ultrasonography are increased in the non-ascitic phase of cirrhosis. Development of ascites is associated with a further increase in these indexes. The resistance indexes are best correlated with severity of hepatocellular dysfunction, assessed by Child score, but not with portal hypertension. Hence, monitoring these indexes, especially PI, is a non-invasive means of studying early renal hemodynamic alteration in childhood cirrhosis.