ISOLATED PROTEINURIA IN CHILDREN - NATURAL-HISTORY AND INDICATIONS FOR RENAL BIOPSY

The significance of isolated proteinuria in pediatric patients is unce rtain. Therefore, we retrospectively studied all children evaluated fo r this urinary abnormality during the 6-year period from 1986 to 1992. Thirty-one patients (19 males), age 2 to 20 years, were identified as having isolated proteinuria that had persisted for a mean interval of 9.6 +/- 1.9 (SEM) months. The diagnosis was based upon the presence o f a urine protein:creatinine ratio >0.2 in an early-morning specimen. None of the patients had hematuria, edema, or azotemia. Seventeen chil dren underwent a renal biopsy. There was no difference between the pat ients who were biopsied and those who were not with respect to age, ma gnitude of proteinuria, glomerular filtration rate (GFR), or serum alb umin and cholesterol concentrations. The renal histopathology revealed focal segmental glomerulosclerosis (FSGS) (n = 8), membranous nephrop athy (n = 1), postinfectious nephritis (n = 2),focal global glomerulos clerosis (FGGS) (n = 1), and normal kidney tissue (n = 5). Twelve of t he patients who did not undergo a kidney biopsy and four of the five c hildren with a normal renal biopsy were followed for at least 12 month s; there was complete resolution of the proteinuria in 11 (69%) of the se patients. The level of proteinuria did not predict the presence or absence of important kidney disease. However, if isolated proteinuria persists for more than 1 year, it is then unlikely to spontaneously re mit and a renal biopsy is indicated to clarify the nature of any under lying glomerulopathy. In children with isolated proteinuria of 1 year' s duration, there is a high likelihood of detecting significant renal pathology that may adversely affect their long-term prognosis.