Excellent - I now have comprehensive content from both Harriet Lane and Rosen's EM. Here is the full synthesis:
Pediatric Proteinuria
Sources: Harriet Lane Handbook (23rd ed.) + Rosen's Emergency Medicine + Campbell-Walsh Urology
1. Definitions (Harriet Lane, p. 701)
| Term | Definition |
|---|
| Orthostatic proteinuria | Protein excretion only when upright; benign, common in children/adolescents |
| Fixed proteinuria | Found on first morning urine on consecutive days; suggests kidney disease |
| Microalbuminuria | Albumin 30-300 mg/g creatinine; below dipstick detection; used for diabetic screening |
| Significant proteinuria | UPr:UCr ratio 0.2-2.0 mg/mg or 4-40 mg/m²/hr on 24-hr collection |
| Nephrotic-range proteinuria | UPr:UCr ratio >2.0 mg/mg or >40 mg/m²/hr on 24-hr collection |
| Nephrotic syndrome | Nephrotic-range proteinuria + hypoalbuminemia + edema + hyperlipidemia (cholesterol >200 mg/dL) |
2. Normal Urine Protein-to-Creatinine Ratio (Harriet Lane / Rosen's)
| Age | Normal UPr:UCr |
|---|
| < 6 months | < 0.5 mg/mg |
| 6 months - 2 years | < 0.5 mg/mg |
| > 2 years | < 0.2 mg/mg |
First morning void UPr:UCr is most accurate. Child must empty bladder before bed and immediately on waking.
3. Dipstick Interpretation (Rosen's EM, Table 168.3)
| Dipstick | mg/dL | Significance |
|---|
| Negative | < 15 | Normal |
| Trace | 15-30 | Transient/benign |
| 1+ | 30-100 | Mild |
| 2+ | 100-300 | Mild-Moderate |
| 3+ | 300-1000 | Moderate-High |
| 4+ | > 1000 | High/Nephrotic range |
False positives: Alkaline or dilute urine, mucus, blood, vaginal/seminal secretions, UTI (Rosen's).
4. Causes of Proteinuria (Harriet Lane Box 19.1 / Rosen's Table 168.4)
Transient (benign)
Fever, exercise, dehydration, cold exposure, seizures, stress, congestive heart failure, recent epinephrine use, hypovolemia, hyperthermia, hypothermia
Orthostatic
Proteinuria only when upright - most common cause in school-age children and adolescents; completely benign
Glomerular Diseases
With isolated proteinuria:
- Idiopathic (minimal change) nephrotic syndrome
- Focal segmental glomerulosclerosis (FSGS)
- Membranous nephropathy
- Membranoproliferative glomerulonephritis
- Diabetic nephropathy, sickle cell nephropathy
With proteinuria as a prominent feature:
- Acute postinfectious GN (post-streptococcal)
- IgA nephropathy
- Henoch-Schonlein Purpura nephritis
- Lupus nephritis
- Alport syndrome
- Reflux nephropathy
Tubular Causes
Heavy metal poisoning (lead, gold, mercury), UTI, Fanconi syndrome, cystinosis, Wilson disease, Lowe syndrome, Dent disease, galactosemia, drugs (aminoglycosides, NSAIDs, cyclosporine, cisplatin), acute tubular necrosis, polycystic kidney disease
5. Clinical Features (Rosen's EM)
- Edema - periorbital (early morning), lower extremities, genital area
- History of preceding streptococcal infection (pharyngitis 1-3 weeks prior, skin 3-6 weeks prior)
- Weight gain from fluid retention
- Decreased urine output
- Joint pain or rash - suggests autoimmune (lupus, HSP)
- Family history of kidney disease or autoimmune conditions
- Blood pressure - hypertension suggests glomerular disease
6. Investigations
For Mild Proteinuria (≤ 2+ on dipstick, Rosen's)
- No emergent workup needed
- Repeat first morning UPr:UCr ratio within 1-2 weeks
- BP monitoring + outpatient PCP follow-up
For Moderate/Significant Proteinuria (≥ 3+ or UPr:UCr > 0.2, Rosen's + Harriet Lane Box 19.2)
| Investigation | Purpose |
|---|
| First morning UPr:UCr ratio | Most accurate quantification |
| Complete metabolic panel (BMP + phosphorus) | Renal function, electrolytes, albumin |
| Serum albumin | Hypoalbuminemia confirms nephrotic syndrome |
| Lipid panel | Hyperlipidemia in nephrotic syndrome |
| C3 and C4 | Low in PSGN, lupus, MPGN |
| ESR, CRP | Inflammation |
| ANA, anti-dsDNA | Lupus nephritis |
| ANCA (c- and p-) | Vasculitic nephritis |
| ASO titer / anti-DNase B | Post-streptococcal GN |
| Hepatitis B, C, HIV | High-risk populations |
| Renal and bladder ultrasound | Anatomic abnormalities (PKD, reflux, obstructive uropathy) |
| Urine culture | Rule out UTI as cause |
7. Management (Rosen's EM + Harriet Lane)
Step 1 - Confirm Proteinuria
Verify dipstick finding with first morning UPr:UCr ratio. A single random dipstick is insufficient.
Step 2 - Rule out Orthostatic Proteinuria
- First morning void: if negative while first morning void is normal -> orthostatic; no further workup needed
- If positive on first morning void -> fixed proteinuria; proceed with evaluation
Step 3 - Stratify by Severity
| Severity | UPr:UCr | Management |
|---|
| Mild (≤2+) | < 0.5 | Repeat UA in 1-2 weeks; PCP follow-up; BP monitoring |
| Moderate (3+) | 0.5-2.0 | Full labs (above), BP monitoring, renal US, nephrology consult |
| Nephrotic range (4+ or UPr:UCr >2) | > 2.0 | Admit + urgent pediatric nephrology consult |
Step 4 - Admission Indications (Rosen's EM)
Admit when any of the following present with significant proteinuria (3+):
- Edema or ascites
- Hypertension > 99th percentile for age/sex/height
- Renal dysfunction (BUN or creatinine elevated > 50% of normal)
- New-onset nephrotic syndrome (most require inpatient; some mild cases outpatient with nephrology guidance)
Step 5 - Treatment of Nephrotic Syndrome (most common cause: Minimal Change Disease)
- Prednisolone 2 mg/kg/day (max 60 mg/day) for 4-6 weeks, then alternate-day dosing
- Fluid restriction for severe edema
- Salt restriction
- Low-dose furosemide for symptomatic edema (with nephrology guidance)
- Monitor for infections (susceptibility to encapsulated organisms due to immunoglobulin loss)
- Pneumococcal vaccination
8. Disposition (Rosen's EM)
- All children with proteinuria - require PCP follow-up with BP monitoring and repeat UA
- Moderate/significant proteinuria - pediatric nephrology consult for renal biopsy decision
- Renal biopsy indicated in: steroid-resistant nephrotic syndrome, age <1 year or >10 years at onset, hematuria + proteinuria, low complement, systemic features
Key Pearls
- Orthostatic proteinuria is the most common cause in school-age children - a first morning UPr:UCr is the single most important test to rule it out
- UPr:UCr > 2.0 = nephrotic range in children over 2 years
- Minimal change disease accounts for ~90% of idiopathic nephrotic syndrome in ages 1-10 years
- Proteinuria + low C3 = think post-streptococcal GN or lupus
- Proteinuria + rash + joint pain = think lupus nephritis or HSP
- Opioids, NSAIDs, aminoglycosides are tubular toxins - always check medication history
Sources: The Harriet Lane Handbook, 23rd ed. (pp. 701-702, Box 19.1, Box 19.2) | Rosen's Emergency Medicine (Ch. 168, Tables 168.3-168.5) | Campbell-Walsh Urology (Ch. 21)