Spot urine samples for evaluating solute excretion in the first week of life
Nephrology Unit,
Department of Paediatrics, University Hospital Centre,
Lausanne, Switzerland
Correspondence to: Professor Jean-Pierre Guignard Unité de Néphrologie, Service de Pédiatrie Centre Hospitalier Universitaire Vaudois 1011 Lausanne, Switzerland. Email: Jean-Pierre.Guignard{at}chuv.hospvd.ch
Accepted 28 October
1998
AIM
To evaluate
whether the urinary creatinine concentration is a reliable reference
value to standardise urinary solute excretion in a spot urine sample
during the first week of life.
METHODSSpontaneously
voided urine specimens were obtained in 48 healthy, full term neonates,
aged 1 to 6 days (median 2.4) and in 168 healthy older children with a
median age of 1.5 years (range 1 month to 3 years). In 62% of the
children two urine samples were available with an interval of 2 to 4 (neonates) and 7 days (older children).
RESULTSIn
neonates both the urinary creatinine concentration and the urinary
creatinine:osmolality ratios were significantly higher than in the
older children, and were spread over a wider range. During the first
postnatal week of life the mean urinary creatinine and urinary
creatinine: osmolality ratio values in the first urine samples were
also significantly higher than in the second samples. In children aged
between 1 month and 3 years of age, these data were remarkably stable
without any significant changes between repeat urine samples.
CONCLUSIONSThe
urinary creatinine concentration during the first days of life is high
and variable, even when corrected for urinary osmolality. This is the
opposite of what is found in older children and adults. Urinary
creatinine and the urinary creatinine:osmolality ratio, therefore,
cannot be used to standardise the urinary excretion of solutes in the
first week of life.
Keywords: spot urine sample; urinary creatinine; osmolality ratio; urinary solute excretion
© 1999 by Archives of Disease in Childhood
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This article has been cited by other articles:
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COULTHARD, M G, HEY, E N, AL-DAHHAN, J, HAYCOCK, G B
(2000). Evaluating urinary flow and solute excretion from urinary creatinine in the first week of life. Arch. Dis. Child. Fetal Neonatal Ed.
82: 257F-257
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