title: Do vesical and voided urine have identical compositions?
abstract: OBJECTIVE
  In view of the concept that the urothelium is a functioning epithelium, we investigated the hypothesis that the composition of urine is modified as it passes through the urethra from the urinary bladder to the exterior.
  
  
  METHODS
  The study was performed in 22 healthy volunteers (13 males, 9 females; mean age 44.6+/-6.2 years). Vesical and voided urine were collected separately; pH was determined using a pH electrode, osmolality by means of micro-osmometry and electrolytes (Na, K) using flame photometry.
  
  
  RESULTS
  Voided urine showed significant increases in pH, osmolality and Na and K concentrations compared to urine contained in the bladder (p < 0.05 for each). Gender and age differences were not significant.
  
  
  CONCLUSIONS
  Vesical urine undergoes changes in some of its components during its passage through the urethra. These findings presumably indicate that the urethral urothelium is a functioning epithelium and also that voided and vesical urine are not identical. The study raises the question to what extent is the analysis of voided urine representative of that of vesical urine?
authors.affiliation: Department of Surgery and Experimental Research, Faculty of Medicine, Cairo University, Cairo, Egypt. shafik@ahmed-shafik.org
authors.forename: Ahmed
authors.initials: A
authors.lastname: Shafik
authors.forename: Olfat
authors.initials: O
authors.lastname: El Sibai
authors.forename: Ali A
authors.initials: AA
authors.lastname: Shafik
authors.forename: Ismail
authors.initials: I
authors.lastname: Ahmed
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D008875:Middle Aged; D009994:Osmolar Concentration; D011188:Potassium / Q000652:urine; D012016:Reference Values; D012964:Sodium / Q000652:urine; D001743:Urinary Bladder / Q000378:metabolism*; D014554:Urination / Q000502:physiology*; D014556:Urine / Q000737:chemistry*
chemical_list: D012964:Sodium; D011188:Potassium