From the Guidelines
Proteinuria in children is primarily caused by glomerular disorders, and the first-line management for nephrotic-range proteinuria involves corticosteroids like prednisone. The etiology of proteinuria in children ranges from benign causes like orthostatic proteinuria to serious conditions such as glomerulonephritis, nephrotic syndrome, or systemic diseases like lupus 1. Management begins with determining the severity through quantification of protein excretion, typically using a urine protein-to-creatinine ratio, with values >0.2 mg/mg in children over 2 years considered abnormal.
Key Points in Management
- Initial evaluation should include a thorough history, physical examination, and urinalysis with microscopy.
- For isolated proteinuria without other symptoms, monitoring with repeat urinalysis in 1-2 weeks is appropriate.
- If proteinuria persists, blood tests including renal function, albumin, and complement levels should be obtained.
- Orthostatic proteinuria, which occurs only when upright, requires no treatment beyond periodic monitoring.
- For nephrotic-range proteinuria (>40 mg/m²/hr or >3.5 g/day), corticosteroids like prednisone at 2 mg/kg/day (maximum 60 mg/day) for 4-6 weeks are typically first-line therapy 1.
- Steroid-resistant cases may require second-line agents such as calcineurin inhibitors (cyclosporine, tacrolimus), mycophenolate mofetil, or rituximab.
- Angiotensin-converting enzyme inhibitors like enalapril (0.1-0.5 mg/kg/day) can reduce proteinuria regardless of cause, as suggested by guidelines 1.
- Dietary sodium restriction and management of hypertension are important supportive measures. The underlying cause determines long-term prognosis, with some conditions resolving completely while others may progress to chronic kidney disease requiring nephrology follow-up.
From the Research
Etiology of Proteinuria in Children
- Proteinuria in children can be categorized as transient, orthostatic, or persistent 2, 3, 4
- Transient proteinuria is temporary and can occur with fever, exercise, stress, or cold exposure, and it resolves when the inciting factor is removed 2
- Orthostatic proteinuria is the most common type in children, especially in adolescent males, and is a benign condition without clinical significance 2, 5
- Persistent proteinuria can be glomerular or tubulointerstitial in origin and may be associated with more serious renal diseases 2, 3
Mechanisms of Proteinuria
- Mechanisms of proteinuria can be categorized as glomerular, tubular, secretory, or overflow 2
- Glomerular proteinuria is associated with diseases that affect the glomeruli, such as nephrotic syndrome 6
- Tubular proteinuria is associated with diseases that affect the tubules, such as tubulointerstitial nephritis 2
Diagnosis of Proteinuria
- The urine dipstick test is the most widely used screening method for proteinuria 2
- A 24-hour urine protein excretion test is usually recommended for quantitation of the amount of protein excreted in the urine, but it may be impractical in children 2, 3
- A spot, first-morning urine test for a protein-to-creatinine or protein-to-osmolality ratio is a reliable substitute for the 24-hour urine protein excretion test 2, 3, 5
Management of Proteinuria
- Treatment of proteinuria should be directed at the underlying cause 2, 3
- Patients with active urinary sediments, hematuria, hypertension, hypocomplementemia, renal insufficiency with depressed glomerular filtration rate, or signs and symptoms suggestive of vasculitic disease may require referral to a pediatric nephrologist and a renal biopsy 2, 3
- Orthostatic proteinuria requires no specific therapy except for health maintenance follow-up 5
- Pediatric nephrologist referral is indicated when the proteinuria is constant and persists over 6 months or is associated with hematuria, hypertension, or renal dysfunction 5