Spot urine samples for evaluating solute excretion in the first week of life

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. METHODS Spontaneously 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). RESULTS In 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. CONCLUSIONS The 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.

[1]  J. Guignard,et al.  Creatinine Reabsorption by the Newborn Rabbit Kidney , 1998, Pediatric Research.

[2]  B. Kasiske,et al.  Use of urine specific gravity to improve screening for albuminuria. , 1997, Kidney international.

[3]  J. Guignard,et al.  Renal Function in Preterm Neonates , 1994, Pediatric Research.

[4]  T. Stukel,et al.  Normal values for random urinary calcium to creatinine ratios in infancy. , 1993, The Journal of pediatrics.

[5]  B. Wilkins,et al.  Renal function in sick very low birthweight infants: 2. Urea and creatinine excretion. , 1992, Archives of disease in childhood.

[6]  P. Griffiths,et al.  Simplified quantification of urinary protein excretion in children. , 1988, Clinical nephrology.

[7]  R. Chevalier,et al.  Prognostic factors in neonatal acute renal failure. , 1984, Pediatrics.

[8]  M. Houser.  Assessment of proteinuria using random urine samples. , 1984, The Journal of pediatrics.

[9]  S. Garella,et al.  Use of single voided urine samples to estimate quantitative proteinuria. , 1983, The New England journal of medicine.

[10]  G. Haycock,et al.  Normal values for plasma creatinine concentration related to maturity in normal term and preterm infants. , 1983, The International journal of pediatric nephrology.

[11]  E. Hughes,et al.  Reference ranges for plasma creatinine during the first month of life. , 1983, Archives of disease in childhood.

[12]  J. Sutphen.  Anthropometric determinants of creatinine excretion in preterm infants. , 1982, Pediatrics.

[13]  J. Guignard,et al.  Plasma creatinine in the first month of life. , 1982, Archives of disease in childhood.

[14]  F. Karlsson,et al.  A PROSPECTIVE STUDY OF URINARY PROTEINS IN EARLY INFANCY , 1979, Acta paediatrica Scandinavica.

[15]  C. Fawer,et al.  Maturation of renal function in full-term and premature neonates. , 1979, Helvetica paediatrica acta.

[16]  J. Guignard,et al.  Renal function in respiratory distress syndrome. , 1976, The Journal of pediatrics.

[17]  J. Guignard,et al.  Glomerular filtration rate in the first three weeks of life. , 1975, The Journal of pediatrics.

[18]  T. Barratt,et al.  Urinary excretion of calcium and magnesium in children , 1974, Archives of disease in childhood.

[19]  J. Scopes,et al.  Rates of creatinine clearance in babies less than one week of age , 1973, Archives of disease in childhood.

[20]  T. Barratt,et al.  Albumin Excretion as a Measure of Glomerular Dysfunction in Children , 1970, Archives of disease in childhood.

[21]  J. Seegmiller,et al.  Urine uric acid to creatinine ratio—a screening test for inberited disorders of purine metabolism , 1968 .

[22]  R. Cort.  Renal Function in the Respiratory Distress Syndrome , 1962, Acta paediatrica.

[23]  B. Nordin.  Assessment of calcium excretion from the urinary calcium/creatinine ratio. , 1959, Lancet.

[24]  P. Vestergaard,et al.  Constancy of urinary creatinine excretion. , 1958, The Journal of laboratory and clinical medicine.

[25]  C. S. Blyth,et al.  Estimation of lean body mass and body fat from basal oxygen consumption and creatinine excretion. , 1952, Journal of applied physiology.