title: Effect of hydration status on renal medulla attenuation on unenhanced CT scans.
abstract: OBJECTIVE
  The purpose of this study was to assess the effect of hydration status on renal medulla attenuation during unenhanced CT.
  
  
  METHODS
  An unenhanced CT scan was obtained in 10 healthy men after 12-18 hr of complete fluid restriction and again after rehydration. CT images were reviewed for the presence and extent of dense renal medulla, defined as greater attenuation than the adjacent cortex. CT findings were correlated with urine-specific gravity and osmolality.
  
  
  RESULTS
  Eight of the 10 subjects showed dense renal medulla on a CT scan after dehydration. After rehydration, complete resolution was seen on the CT scan in four of the eight subjects; three of the eight subjects showed a decrease in the extent of dense renal medulla. After rehydration, the eighth subject showed a slight increase in the attenuation of the renal medulla on the CT scan. Dense renal medulla was seen significantly more often on dehydration images (p = .035).
  
  
  CONCLUSIONS
  Increased renal medulla attenuation on an unenhanced CT scan can be a normal finding related to dehydration.
authors.affiliation: Department of Radiology, Albany Medical College, NY 12208, USA.
authors.forename: M E
authors.initials: ME
authors.lastname: Tublin
authors.forename: F N
authors.initials: FN
authors.lastname: Tessler
authors.forename: T R
authors.initials: TR
authors.lastname: McCauley
authors.forename: C D
authors.initials: CD
authors.lastname: Kesack
mesh_terms: D000328:Adult; D003681:Dehydration; D006801:Humans; D007679:Kidney Medulla / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D014057:Tomography, X-Ray Computed