Chapter 16. Nephrology

Clinical Summary

Healthy children normally have protein in their urine, at a rate of protein excretion <4 mg/m2/h or <100 mg/m2/d throughout childhood. The upper limit of normal protein excretion is up to 150 mg/d. Albumin, relatively small in molecular size, tends to be the dominant constituent, and Tamm-Horsfall protein, a mucoprotein produced in the distal tubule, makes up the remainder.

Proteinuria in children can be transient, orthostatic, or pathologic. Transient proteinuria (often associated with fever, stress, dehydration, or exercise) does not indicate underlying renal disease. Orthostatic proteinuria (elevated protein excretion when the subject is upright but normal protein excretion during recumbency) occurs most commonly in school-aged children and rarely exceeds 1 g/m/d. These patients do not have hematuria and have normal values of creatinine clearance and C3 complement. Pathologic proteinuria is likely if proteinuria is associated with hematuria and/or the first morning urine Pr/Cr ratio is >0.2 in older children. Nephrotic-range proteinuria is levels >40 mg/m/h in 24 hours.

Emergency Department Treatment and Disposition

Take a complete history and physical examination including blood pressure in a patient with proteinuria. In general, urinalysis showing mild proteinuria (trace to 1+) is not reliable during acute illness (unless there are other symptoms and signs pointing to renal disease). Discharge patients with mild proteinuria who have normal blood pressure and urine output and no evidence of kidney disease. For patients with moderate to severe proteinuria (3+ or 4+), obtain serum albumin, creatinine, cholesterol, electrolytes, serum C3/C4 complement, antinuclear antibody, serologies for hepatitis B and C, and human immunodeficiency virus as clinically indicated. Use renal ultrasound to exclude underlying renal disease. Consult pediatric nephrology for further evaluation if any of the studies are abnormal. Hospitalize patients with severe nephrosis, especially the first episode.

Pearls

1. Not all proteinuria is pathologic.

2. Exclude hematuria when evaluating patients with proteinuria in the emergency department (ED).

3. Proteinuria is not an uncommon finding in children and may indicate a completely benign condition or be the first clue to a significant renal parenchymal disease (eg, nephrotic syndrome or glomerulonephritis).

4. Heavy proteinuria (3+ or 4+ on dipstick) is typically seen in nephrotic syndrome; mild proteinuria (trace to 1+) is typically seen with fever or dehydration.