Obesity-Related Nephropathy in Children

Carolyn L. Abitbol; Maria M. Rodríguez


Pediatr Health. 2009;3(2):141-153. 

In This Article

Proteinuria and Microalbuminuria

Proteinuria is the most important early predictor of renal injury by current standards. As with the Ccr, 24-h urine collections to evaluate total protein excretion has been replaced in pediatric practice with random urine total protein:creatinine (Upr/cr) and urine albumin:creatinine (Ualb/cr) ratios.[108] Multiple studies in adults and children have validated the use of randomly voided samples to estimate the total protein excretion in individuals.[108,109] Normal proteinuria is defined as an excretion of less than 150 mg/day of total protein and less than 30 mg/day of albumin. In children, normal proteinuria is reflected by a random Upr/cr less than or equal to 0.2 mg/mg while nephrotic range proteinuria is greater than or equal to 2.0 mg/mg, respectively.[108,109] These ratios are consistent with a daily protein excretion of less than 100 mg/m2/day and more than 1000 mg/m2/day.[108,109] It is important to note that the routine urinalysis used in the pediatrician's office practice cannot estimate daily protein excretion. Urinary dipsticks detect only albuminuria at a concentration in excess of 300 mg/dl. Moreover, low molecular-weight proteinuria, which is the non-albumin component of proteinuria, cannot be detected by the urinary protein dipstick and requires quantitation by the urine total protein method.[108,109] Although less studied in adults, the non-albumin component of proteinuria is frequent in pediatric patients, particularly those with congenital renal disease and interstitial nephropathies.[109] This may be especially important in obese patients who frequently present with heavy proteinuria, normal serum proteins and the absence of edema, suggesting a unique mix of proteinuria that may be dominated by non-albumin proteinuria.[109]