Renal resistive index and long-term outcome in chronic nephropathies.
OBJECTIVE
To assess the clinical validity of renal resistive index (RI) to determine prognosis and guide therapy over a long-term follow-up in patients with chronic nephropathies and to verify the commonly used threshold value of 0.70.


METHODS
Of patients referred to the nephrology center since 1995, 177 were initially enrolled and 86 were followed up for RI and renal function annually for 2-11 years (mean, 5.93 years +/- 2.92 [standard deviation]). All patients gave informed consent for the institutional review board-approved study. Correlations were determined between initial RI and age, estimated glomerular filtration rate (eGFR), proteinuria, hematuria, blood pressure, and biopsy scores. The sample was categorized in four groups on the basis of whether initial values of RI and eGFR were normal, and progression to renal failure was compared. With grouping of the sample by using initial RI (< or =0.61, 0.62-0.69, and > or =0.70), Kaplan-Meier analysis was used to obtain survival curves.


RESULTS
Initial RI correlated with final eGFR (R = -0.4, P < .001), systolic blood pressure (R = 0.39, P < .001), proteinuria (R = 0.28, P = .009), and age (R = 0.28, P = .007). In stepwise multiple regression analysis, RI emerged as the only independent risk factor for the progression to renal failure (P < .001). Among the four groups of patients with different initial RIs and eGFRs, the group with an initial RI of 0.70 or higher showed a worse outcome, independent of initial eGFR. In the Kaplan-Meier analysis by using initial RI, only the group with a value of 0.70 or higher showed a rapid decline of renal function (>50% decrease in eGFR in 6 years).


CONCLUSIONS
An RI of 0.70 or higher is predictive of an unfavorable outcome in patients with chronic nephropathies.
Parolini
Claudia
C
Department of Nephrology, Tor Vergata University, Viale Oxford 81, 00133 Rome, Italy. claudiaparolini.parolini@gmail.com
Noce
Annalisa
A
Staffolani
Emiliano
E
Giarrizzo
Gerlando F
GF
Costanzi
Stefano
S
Splendiani
Giorgio
G
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016009:Chi-Square Distribution; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology; D006801:Humans; D007676:Kidney Failure, Chronic / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D007677:Kidney Function Tests; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D012044:Regression Analysis; D012307:Risk Factors; D015996:Survival Rate; D014463:Ultrasonography