title: Renal arterial resistive index is associated with severe histological changes and poor renal outcome during chronic kidney disease.
abstract: BACKGROUND
  Chronic kidney disease (CKD) is a growing public health problem and end stage renal disease (ESRD) represents a large human and economic burden. It is important to identify patients at high risk of ESRD. In order to determine whether renal Doppler resistive index (RI) may discriminate those patients, we analyzed whether RI was associated with identified prognosis factors of CKD, in particular histological findings, and with renal outcome.
  
  
  METHODS
  RI was measured in the 48 hours before renal biopsy in 58 CKD patients. Clinical and biological data were collected prospectively at inclusion. Arteriosclerosis, interstitial fibrosis and glomerulosclerosis were quantitatively assessed on renal biopsy in a blinded fashion. MDRD eGFR at 18 months was collected for 35 (60%) patients. Renal function decline was defined as a decrease in eGFR from baseline of at least 5 mL/min/ 1.73 m2/year or need for chronic renal replacement therapy. Pearson's correlation, Mann-Whitney and Chi-square tests were used for analysis of quantitative and qualitative variables respectively. Kaplan Meier analysis was realized to determine renal survival according to RI value using the log-rank test. Multiple logistic regression was performed including variables with p < 0.20 in univariate analysis.
  
  
  RESULTS
  Most patients had glomerulonephritis (82%). Median age was 46 years [21-87], eGFR 59 mL/min/ 1.73m2 [5-130], percentage of interstitial fibrosis 10% [0-90], glomerulosclerosis 13% [0-96] and RI 0.63 [0.31-1.00]. RI increased with age (r = 0.435, p = 0.0063), pulse pressure (r = 0.303, p = 0.022), renal atrophy (r = -0.275, p = 0.038) and renal dysfunction (r = -0.402, p = 0.0018). Patients with arterial intima/media ratio ≥ 1 (p = 0.032), interstitial fibrosis > 20% (p = 0.014) and renal function decline (p = 0.0023) had higher RI. Patients with baseline RI ≥ 0.65 had a poorer renal outcome than those with baseline RI < 0.65 (p = 0.0005). In multiple logistic regression, RI≥0.65 was associated with accelerated renal function decline independently of baseline eGFR and proteinuria/creatininuria ratio (OR=13.04 [1.984-85.727], p = 0.0075). Sensitivity, specificity, predictive positive and predictive negative values of RI ≥ 0.65 for renal function decline at 18 months were respectively 77%, 86%, 71% and 82%.
  
  
  CONCLUSIONS
  Our results suggest that RI ≥ 0.65 is associated with severe interstitial fibrosis and arteriosclerosis and renal function decline. Thus, RI may contribute to identify patients at high risk of ESRD who may benefit from nephroprotective treatments.
authors.affiliation: Department of Nephrology, AP-HP, Hôpital Tenon, 4 rue de la Chine, Paris, F-75020, France. naikebige@gmail.com
authors.forename: Naïke
authors.initials: N
authors.lastname: Bigé
authors.forename: Pierre Patrick
authors.initials: PP
authors.lastname: Lévy
authors.forename: Patrice
authors.initials: P
authors.lastname: Callard
authors.forename: Jean-Manuel
authors.initials: JM
authors.lastname: Faintuch
authors.forename: Valérie
authors.initials: V
authors.lastname: Chigot
authors.forename: Virginie
authors.initials: V
authors.lastname: Jousselin
authors.forename: Pierre
authors.initials: P
authors.lastname: Ronco
authors.forename: Jean-Jacques
authors.initials: JJ
authors.lastname: Boffa
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology; D006801:Humans; D053208:Kaplan-Meier Estimate; D007668:Kidney / Q000098:blood supply* / Q000473:pathology*; D007676:Kidney Failure, Chronic / Q000473:pathology* / Q000503:physiopathology; D007677:Kidney Function Tests / Q000379:methods; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012077:Renal Artery / Q000473:pathology* / Q000503:physiopathology; D051436:Renal Insufficiency, Chronic / Q000473:pathology* / Q000503:physiopathology; D012720:Severity of Illness Index; D016037:Single-Blind Method; D016896:Treatment Outcome; D014655:Vascular Resistance / Q000502:physiology*; D055815:Young Adult