title: Renal resistive index as an indicator of the presence and severity of anemia and its future development in patients with hypertension.
abstract: BACKGROUND
  We examined whether renal resistive index (RI), a simple index of renal vascular resistance, is associated with the presence and severity of anemia, and can predict the future development of anemia in patients with hypertension.
  
  
  METHODS
  We retrospectively examined 175 patients with hypertension (mean age 67 ± 11 years, 32-85 years, 134 males) who underwent renal ultrasonography. Anemia was defined as a reduction in the concentration of hemoglobin <13.0 g/dL for men and <12.0 g/dL for women. Renal RI was measured in the interlobar arteries.
  
  
  RESULTS
  Anemia was present in 37% of men and 34% of women. The mean estimated glomerular filtration rate (eGFR) was 58 ± 23 ml/min/1.73 m(2) (median: 56 ml/min/1.73 m(2), range: 16-168 ml/min/1.73 m(2)) and the mean renal RI was 0.70 ± 0.09 (median: 0.70, range: 0.45-0.92). Proteinuria was present in 29% of patients. Both eGFR and renal RI correlated significantly with hemoglobin levels. In the stepwise multivariate linear regression analysis, renal RI was associated with hemoglobin levels independently of potential confounders including eGFR. During the follow-up period (median: 959 days, range: 7-3595 days), Kaplan-Meier curves demonstrated that patients with renal RI above the median value had a higher incidence of the future development of anemia than other patients. Cox regression analysis showed that renal RI (hazard ratio 1.18, 95% CI 1.02-1.37 per 0.05 rises in renal RI, p =0.03) and the presence of proteinuria were (hazard ratio 1.80, 95% CI 1.08-3.01, p =0.03) were independently associated with the future development of anemia after correcting for confounding factors.
  
  
  CONCLUSIONS
  Measurement of renal RI can be useful for elucidating the pathogenesis of anemia and for inferring its potential risk in patients with hypertension.
authors.affiliation: Department of Cardiology and Nephrology, Mie University Graduate School of Medicine, Tsu, Japan. m-tanimura@clin.medic.mie-u.ac.jp.
authors.forename: Muneyoshi
authors.initials: M
authors.lastname: Tanimura
authors.affiliation: Department of Cardiology and Nephrology, Mie University Graduate School of Medicine, Tsu, Japan. dohik@clin.medic.mie-u.ac.jp.
authors.forename: Kaoru
authors.initials: K
authors.lastname: Dohi
authors.affiliation: Central Clinical Laboratories, Mie University Hospital, Tsu, Japan. mandms@clin.medic.mie-u.ac.jp.
authors.forename: Masumi
authors.initials: M
authors.lastname: Matsuda
authors.affiliation: Department of Cardiology and Nephrology, Mie University Graduate School of Medicine, Tsu, Japan. sato0726@clin.medic.mie-u.ac.jp.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Sato
authors.affiliation: Department of Cardiology and Nephrology, Mie University Graduate School of Medicine, Tsu, Japan. emyogw@gmail.com.
authors.forename: Emiyo
authors.initials: E
authors.lastname: Sugiura
authors.affiliation: Department of Cardiology and Nephrology, Mie University Graduate School of Medicine, Tsu, Japan. kuma_cuma@yahoo.co.jp.
authors.forename: Naoto
authors.initials: N
authors.lastname: Kumagai
authors.affiliation: Department of Cardiology and Nephrology, Mie University Graduate School of Medicine, Tsu, Japan. n-shiro@clin.medic.mie-u.ac.jp.
authors.forename: Shiro
authors.initials: S
authors.lastname: Nakamori
authors.affiliation: Department of Translational Medical Science, Mie University Graduate School of Medicine, Tsu, Japan. t-yamada@doc.medic.mie-u.ac.jp.
authors.forename: Tomomi
authors.initials: T
authors.lastname: Yamada
authors.affiliation: Department of Molecular and Laboratory Medicine, Mie University Graduate School of Medicine, Tsu, Japan. naokifujimo@hotmail.com.
authors.forename: Naoki
authors.initials: N
authors.lastname: Fujimoto
authors.affiliation: Department of Cardiology and Nephrology, Mie University Graduate School of Medicine, Tsu, Japan. t-tanigw@clin.medic.mie-u.ac.jp.
authors.forename: Takashi
authors.initials: T
authors.lastname: Tanigawa
authors.affiliation: Department of Cardiology and Nephrology, Mie University Graduate School of Medicine, Tsu, Japan. n-yamada@clin.medic.mie-u.ac.jp.
authors.forename: Norikazu
authors.initials: N
authors.lastname: Yamada
authors.affiliation: Department of Cardiology and Nephrology, Mie University Graduate School of Medicine, Tsu, Japan. mashio@clin.medic.mie-u.ac.jp.
authors.forename: Mashio
authors.initials: M
authors.lastname: Nakamura
authors.affiliation: Department of Cardiology and Nephrology, Mie University Graduate School of Medicine, Tsu, Japan. mitoka@clin.medic.mie-u.ac.jp.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Ito
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000740:Anemia / Q000453:epidemiology / Q000209:etiology* / Q000503:physiopathology; D015331:Cohort Studies; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D005919:Glomerular Filtration Rate / Q000502:physiology; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D006973:Hypertension / Q000453:epidemiology / Q000503:physiopathology*; D007564:Japan; D053208:Kaplan-Meier Estimate; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D015588:Observer Variation; D016016:Proportional Hazards Models; D011507:Proteinuria / Q000175:diagnosis* / Q000453:epidemiology; D012078:Renal Artery Obstruction / Q000000981:diagnostic imaging* / Q000503:physiopathology; D012189:Retrospective Studies; D018570:Risk Assessment; D012737:Sex Factors; D018608:Ultrasonography, Doppler; D014655:Vascular Resistance / Q000502:physiology*
chemical_list: D006454:Hemoglobins