Renal concentrating capacity as a marker for glomerular filtration rate.
OBJECTIVE
We have studied 160 children with a variety of renal diseases, 14 of them with chronic renal failure (CRF), to evaluate maximum urinary osmolality as a predictor of glomerular filtration rate (GFR) testing the hypothesis that a normal GFR is necessary to have a normal urinary concentrating capacity.


METHODS
All patients had a serum creatinine measured. GFR was calculated according to the Schwartz formula. All patients underwent desmopressin (DDAVP) test to evaluate renal concentrating capacity.


RESULTS
Patients with CRF were unable to concentrate the urine beyond 486 mosm/kg whereas all patients with a normal concentrating capacity (urine osmolality >835 mosm/kg) had a normal GFR. Desmopressin test sensitivity to detect CRF was 100% and specificity 70.5%. A significant negative correlation was found between urinary osmolality after DDAVP administration and serum creatinine levels and between urinary volume corrected by 100 mL of GFR (V/GFR) and urinary osmolality.


CONCLUSIONS
In our series, a normal concentrating capacity was always associated with a normal GFR while all patients with decreased GFR had a concentrating capacity defect. Thus, in the evaluation of infants and children with renal disease, the finding of a normal urinary concentrating capacity will suggest and intact glomerular and tubular function.
García Nieto
Víctor M
VM
Unidad de Nefrología Pediátrica, Hospital Universitario Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Spain. vgarcianieto@gmail.com
Yanes
María Isabel Luis
MI
Zamorano
Margarita Monge
MM
González
Maria José Hernández
MJ
Aros
Carolina Peralta
CP
Garin
Eduardo H
EH
D000293:Adolescent; D000328:Adult; D015415:Biomarkers; D002648:Child; D002675:Child, Preschool; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007671:Kidney Concentrating Ability; D007674:Kidney Diseases / Q000503:physiopathology*; D008297:Male; D011237:Predictive Value of Tests
D015415:Biomarkers