title: Evaluation of Renal Blood Flow and Oxygenation in CKD Using Magnetic Resonance Imaging.
abstract: BACKGROUND
  Animal studies suggest that progression of chronic kidney disease (CKD) is related to renal hypoxia. With renal blood supply determining oxygen delivery and sodium absorption being the main contributor to oxygen consumption, we describe the relationship between renal oxygenation, renal artery blood flow, and sodium absorption in patients with CKD and healthy controls.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  62 stable patients with CKD stages 3 to 4 (mean age, 61±13 [SD] years) and 24 age- and sex-matched controls.
  
  
  METHODS
  CKD versus control status.
  
  
  RESULTS
  Renal artery blood flow, tissue oxygenation (relative changes in deoxyhemoglobin concentration of the renal medulla [MR2*] and cortex [CR2*]), and sodium absorption.
  
  
  METHODS
  Renal artery blood flow was determined by phase-contrast magnetic resonance imaging (MRI); MR2* and CR2* were determined by blood oxygen level-dependent MRI. Ultrafiltered and reabsorbed sodium were determined from measured glomerular filtration rate (mGFR) and 24-hour urine collections.
  
  
  RESULTS
  mGFR in patients was 37% that of controls (36±15 vs 97±23 mL/min/1.73 m(2); P < 0.001), and reabsorbed sodium was 37% that of controls (6.9 vs 19.1 mol/24 h; P < 0.001). Single-kidney patient renal artery blood flow was 72% that of controls (319 vs 443 mL/min; P < 0.001). Glomerular filtration fraction was 9% in patients and 18% in controls (P < 0.001). Patients and controls had similar CR2* (13.4 vs 13.3 s(-1)) and medullary MR2* (26.4 vs 26.5 s(-1)) values. Linear regression analysis demonstrated no associations between R2* and renal artery blood flow or sodium absorption. Increasing arterial blood oxygen tension by breathing 100% oxygen had very small effects on CR2*, but reduced MR2* in both groups.
  
  
  CONCLUSIONS
  Only renal artery blood flow was determined and thus regional perfusion could not be related to CR2* or MR2*.
  
  
  CONCLUSIONS
  In CKD, reductions of mGFR and reabsorbed sodium are more than double that of renal artery blood flow, whereas cortical and medullary oxygenation are within the range of healthy persons. Reduction in glomerular filtration fraction may prevent renal hypoxia in CKD.
authors.affiliation: Department of Renal Medicine, Aarhus University Hospital, Aarhus, Denmark. Electronic address: dinah.khatir@clin.au.dk.
authors.forename: Dinah S
authors.initials: DS
authors.lastname: Khatir
authors.affiliation: MR Research Centre, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Michael
authors.initials: M
authors.lastname: Pedersen
authors.affiliation: Department of Renal Medicine, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Bente
authors.initials: B
authors.lastname: Jespersen
authors.affiliation: Department of Renal Medicine, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Niels H
authors.initials: NH
authors.lastname: Buus
mesh_terms: D000368:Aged; D003430:Cross-Sectional Studies; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007668:Kidney / Q000098:blood supply*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption / Q000502:physiology; D012039:Regional Blood Flow; D051436:Renal Insufficiency, Chronic / Q000503:physiopathology*; D065608:Renal Reabsorption / Q000502:physiology*; D012964:Sodium / Q000378:metabolism*
chemical_list: D012964:Sodium; D010100:Oxygen
keywords: Renal hypoxia; blood oxygen level−dependent (BOLD) MRI; chronic kidney disease (CKD); glomerular filtration rate (GFR); kidney disease progression; magnetic resonance imaging (MRI); renal artery blood flow; renal tissue oxygenation; sodium absorption