title: Defining hypercalciuria in nephrolithiasis.
abstract: The classic definition of hypercalciuria, an upper normal limit of 200  mg/day, is based on a constant diet restricted in calcium, sodium, and animal protein; however, random diet data challenge this. Here our retrospective study determined the validity of the classic definition of hypercalciuria by comparing data from 39 publications analyzing urinary calcium excretion on a constant restricted diet and testing whether hypercalciuria could be defined when extraneous dietary influences were controlled. These papers encompassed 300 non-stone-forming patients, 208 patients with absorptive hypercalciuria type I (presumed due to high intestinal calcium absorption), and 234 stone formers without absorptive hypercalciuria; all evaluated on a constant restricted diet. In non-stone formers, the mean urinary calcium was well below 200  mg/day, and the mean for all patients was 127±46  mg/day with an upper limit of 219  mg/day. In absorptive hypercalciuria type I, the mean urinary calcium significantly exceeded 200  mg/day in all studies with a combined mean of 259±55  mg/day. Receiver operating characteristic curve analysis showed the optimal cutoff point for urinary calcium excretion was 172  mg/day on a restricted diet, a value that approximates the traditional limit of 200  mg/day. Thus, on a restricted diet, a clear demarcation was seen between urinary calcium excretion of kidney stone formers with absorptive hypercalciuria type I and normal individuals. When dietary variables are controlled, the classic definition of hypercalciuria of nephrolithiasis appears valid.
authors.affiliation: Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390-8885, USA.
authors.forename: Charles Y C
authors.initials: CY
authors.lastname: Pak
authors.forename: Khashayar
authors.initials: K
authors.lastname: Sakhaee
authors.forename: Orson W
authors.initials: OW
authors.lastname: Moe
authors.forename: John
authors.initials: J
authors.lastname: Poindexter
authors.forename: Beverley
authors.initials: B
authors.lastname: Adams-Huet
authors.forename: Margaret S
authors.initials: MS
authors.lastname: Pearle
authors.forename: Joseph E
authors.initials: JE
authors.lastname: Zerwekh
authors.forename: Glenn M
authors.initials: GM
authors.lastname: Preminger
authors.forename: Michael R
authors.initials: MR
authors.lastname: Wills
authors.forename: Neil A
authors.initials: NA
authors.lastname: Breslau
authors.forename: Fredric C
authors.initials: FC
authors.lastname: Bartter
authors.forename: D C
authors.initials: DC
authors.lastname: Brater
authors.forename: Howard J
authors.initials: HJ
authors.lastname: Heller
authors.forename: Clarita V
authors.initials: CV
authors.lastname: Odvina
authors.forename: Cindy L
authors.initials: CL
authors.lastname: Wabner
authors.forename: John S
authors.initials: JS
authors.lastname: Fordtran
authors.forename: Man
authors.initials: M
authors.lastname: Oh
authors.forename: Abhimanyu
authors.initials: A
authors.lastname: Garg
authors.forename: Jean A
authors.initials: JA
authors.lastname: Harvey
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Alpern
authors.forename: William H
authors.initials: WH
authors.lastname: Snyder
authors.forename: Paul C
authors.initials: PC
authors.lastname: Peters
mesh_terms: D002118:Calcium / Q000652:urine*; D006801:Humans; D053565:Hypercalciuria / Q000150:complications / Q000175:diagnosis* / Q000178:diet therapy / Q000652:urine; D053040:Nephrolithiasis / Q000150:complications / Q000178:diet therapy / Q000652:urine*; D012372:ROC Curve; D012189:Retrospective Studies
chemical_list: D002118:Calcium