Work up for nephrotic syndrome
What is the appropriate work up for patients with nephrotic syndrome?
• Patients with primary nephrotic syndrome require quantitation of urine protein excretion to demonstrate nephrotic-range proteinuria. This can be accomplished by measuring the protein:creatinine ratio in the first morning urine specimen where a value >2 (mg:mg) in children is indicative of nephrotic syndrome. Alternatively, in adults, a 24-hour urine collection can be performed, and a level of protein in excess of 3.5 g is diagnostic of nephrotic-range proteinuria. While assessment of the first morning urine specimen is the standard of care in pediatric patients, there is greater diversity of practice in adult patient, with use of first morning urine samples, spot urine specimens, and 24-hour urine collections to monitor disease activity.
• A complete metabolic profile is obtained to demonstrate hypoalbuminemia and hypercholesterolemia. The blood urea nitrogen and creatinine are generally normal. Total serum calcium level is low secondary to the low hypoalbuminemia. Serum sodium concentration may be low if there is water reabsorption in excess of sodium. Pseudohyponatremia secondary to hyperlipidemia is no longer a concern with the widespread use of ion selective electrodes in clinical chemistry analyzers.
• The C3 level is measured in all patients to exclude MPGN.
• A complete blood count is part of the routine evaluation even though it usually has little information value about the cause of nephrotic syndrome. In select cases in which the nephrotic syndrome is secondary to a systemic illness or malignancy, the complete blood count may provide useful data.