title: Renal oxygenation changes during acute unilateral ureteral obstruction: assessment with blood oxygen level-dependent mr imaging--initial experience.
abstract: OBJECTIVE
  To prospectively determine if changes in intrarenal oxygenation during acute unilateral ureteral obstruction can be depicted with blood oxygen level-dependent (BOLD) magnetic resonance (MR) imaging.
  
  
  METHODS
  The study was approved by the local ethics committee, and written informed consent was obtained from all patients. BOLD MR imaging was performed in 10 male patients (mean age, 45 years +/- 17 [standard deviation]; range, 20-73 years) with a distal unilateral ureteral calculus and in 10 healthy age-matched male volunteers to estimate R2*, which is inversely related to tissue Po(2). R2* values were determined in the cortex and medulla of the obstructed and the contralateral nonobstructed kidneys. To reduce external effects on R2*, the R2* ratio between the medulla and cortex was also analyzed. Statistical analysis was performed with nonparametric rank tests. P < .05 was considered to indicate a significant difference.
  
  
  RESULTS
  All patients had significantly lower medullary and cortical R2* values in the obstructed kidney (median R2* in medulla, 10.9 sec(-1) [range, 9.1-14.3 sec(-1)]; median R2* in cortex, 10.4 sec(-1) [range, 9.7-11.3 sec(-1)]) than in the nonobstructed kidney (median R2* in medulla, 17.2 sec(-1) [range, 14.6-23.2 sec(-1)], P = .005; median R2* in cortex, 11.7 sec(-1) [range, 11.0-14.0 sec(-1)], P = .005); values in the obstructed kidneys were also significantly lower than values in the kidneys of healthy control subjects (median R2* in medulla, 16.1 sec(-1) [range, 13.9-18.1 sec(-1)], P < .001; median R2* in cortex, 11.6 sec(-1) [range, 10.5-12.9 sec(-1)], P < .001). R2* ratios in the obstructed kidneys (median, 1.06; range, 0.85-1.27) were significantly lower than those in the nonobstructed kidneys (median, 1.49; range, 1.26-1.71; P = .005) and those in the kidneys of healthy control subjects (median, 1.38; range, 1.23-1.47; P < .001). In contrast, R2* ratios in the nonobstructed kidneys of patients were significantly higher than those in kidneys of healthy control subjects (P = .01).
  
  
  CONCLUSIONS
  Increased oxygen content in the renal cortex and medulla occurs with acute unilateral ureteral obstruction, suggesting reduced function of the affected kidney.
authors.affiliation: Department of Radiology, Neuroradiology and Nuclear Medicine, University Hospital of Bern, Inselspital, Freiburgstrasse 10, CH-3010 Bern, Switzerland. Harriet.Thoeny@insel.ch
authors.forename: Harriet C
authors.initials: HC
authors.lastname: Thoeny
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Kessler
authors.forename: Sonia
authors.initials: S
authors.lastname: Simon-Zoula
authors.forename: Frederik
authors.initials: F
authors.lastname: De Keyzer
authors.forename: Markus
authors.initials: M
authors.lastname: Mohaupt
authors.forename: Urs E
authors.initials: UE
authors.lastname: Studer
authors.forename: Peter
authors.initials: P
authors.lastname: Vermathen
mesh_terms: D000208:Acute Disease; D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007668:Kidney / Q000378:metabolism*; D016014:Linear Models; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000378:metabolism*; D018709:Statistics, Nonparametric; D036542:Tomography, Spiral Computed; D014517:Ureteral Obstruction / Q000175:diagnosis* / Q000378:metabolism
chemical_list: D010100:Oxygen