Orthostatic proteinuria accounts for up to 60 percent of all cases of asymptomatic proteinuria reported in children, with an even higher incidence in adolescents. 18 Variations in the quantity of daily protein excretion have been observed. If all laboratory tests are normal except for persistently elevated protein excretion, the possibility of orthostatic proteinuria should be investigated, particularly if the child is older than six years of age. This is best done by using the so-called orthostatic test. The patient is instructed to urinate just before going to bed at night and to discard the urine. He or she must remain supine all night and urinate the next morning immediately after arising. This urine sample is kept separate and labeled “supine” or “recumbent.”
The family can be reassured if the proteinuria is transient or orthostatic, and the child is asymptomatic, has no associated hematuria, and has normal blood pressure and glomerular filtration rate. Regular follow-up is important, however, as long as significant proteinuria persists. Although there are no formal guidelines for monitoring, a child with persistent proteinuria should initially receive a physical examination, blood pressure measurement, urinalysis, and blood tests for creatinine and urea nitrogen levels every six to 12 months. 29 There is no specific limitation on diet or physical activity. Once the child is stable, follow-up can be annual.