title: A modification of the urine osmolal gap: an improved method for estimating urine ammonium.
abstract: A modification of the urine osmolal gap was evaluated as an estimate of urine [NH4+]. We proposed that: Urine [NH4+] = Urine osmolality - [2(Na+ + K+) + urea + glucose]/2 Spot urine samples were collected from normal volunteers and from individuals with ketonuria; the modified urine osmolal gap as well as two other previously described estimates of urine [NH4+] were compared with measured urine [NH4+]. There was a significant positive linear correlation between the urine [NH4+] and the modified urine osmolal gap in normal volunteers (r = 0.81; p less than 0.01) and in individuals with ketonuria (r = 0.93; p less than 0.001). The originally described urine osmolal gap greatly overestimated the urine [NH4+] but also showed a significant correlation. The urine anion gap was not a valid estimate of urine [NH4+] within the range of values measured in our subjects. The modified urine osmolal gap is an improvement over previously described estimates of urine [NH4+] and can be used as a single calculation in place of the other two.
authors.affiliation: Department of Medicine, University of Saskatchewan, Saskatoon, Canada.
authors.forename: R F
authors.initials: RF
authors.lastname: Dyck
authors.forename: S
authors.initials: S
authors.lastname: Asthana
authors.forename: J
authors.initials: J
authors.lastname: Kalra
authors.forename: M L
authors.initials: ML
authors.lastname: West
authors.forename: K L
authors.initials: KL
authors.lastname: Massey
mesh_terms: D000136:Acid-Base Equilibrium; D000138:Acidosis / Q000652:urine*; D000641:Ammonia / Q000652:urine*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007657:Ketone Bodies / Q000652:urine*; D009994:Osmolar Concentration
chemical_list: D007657:Ketone Bodies; D000641:Ammonia