Abstract Book - 26th ESPU Congress, Joint Meeting with ICCS + SPU + AAP/SOU + AAPU + SFU

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ICCS S3-14 (P)
AN INCREASE IN URINE VOLUME IS ASSOCIATED WITH AN INCREASE IN
URINARY SODIUM AND CALCIUM BUT A FALL IN SUPERSATURATION OF
CALCIUM OXALATE.
Elizabeth JACKSON1, Ahtyanna KENDRICK2, Marion SCHULTE 2, William DEFOOR1 and Prasad DEVARAJAN2
1) Cincinnati Children's Hospital Medical Center, Urology, Cincinnati, USA - 2) Cincinnati Children's Hospital Medical
Center, Nephrology, Cincinnati, USA
PURPOSE
To investigate the relationship between urine sodium, calcium, and supersaturation of calcium oxalate (SS CaOx) in
children as urine volume changed on consecutive days.
MATERIAL AND METHODS
We evaluated two 24-hour urinary metabolic stone profiles performed on consecutive days in 304 children. The urinary
metabolic stone profiles were performed by Litholink Corporation. Since children vary in size, total urinary sodium and
calcium were converted to mg/kg/day. The difference from the first day to the second day was plotted against the
change in urine volume in ml/kg/day from day 1 to day 2. A subset of children with the greatest change in urine
volume but similar urine creatinines was evaluated separately.
RESULTS
On average each 10ml/kg/day rise in urine volume was associated with a rise in urine sodium of 0.8mg/kg/day
Each 10ml/kg/day rise in urine volume was associated with a rise in urine calcium of approximately 0.7mg/kg/day.
Each 10ml/kg/day rise in urine volume was associated with a fall in supersaturation of calcium oxalate (SS CaOx) of
17.5%
Could the change in volume and calcium be secondary to an increase in dietary and thus
urinary sodium? To address this concern, we evaluated 27 children whose volume varied by more than 40% between 2
consecutive days but whose urine creatinines were similar.
This significant change in volume is unlikely to be due to increased dietary sodium. In 19 children the higher urine
volume was associated with a higher urine sodium and calcium but an improvement in SS CaOx.
CONCLUSIONS
Increasing urine volume is associated with higher urine sodium and calcium but lower urine SS CaOx. When children
acutely change urine volume, there may be an increase in urine sodium and calcium that does not reflect dietary
indiscretions but rather intravascular expansion. Despite a rise is sodium and calcium, in increase in urine volume
usually leads to improved SSCaOx.