Proteinuria

Proteinuria: Excerpt from In A Page: Pediatric Signs and Symptoms

Proteinuria in children is defined as a quantitative 24-hour urine collection with >4 mg/m²/hour (>100 mg/m²/day) of protein. Semiquantitative definitions include urine dipstick ≥1+ (30 mg/dL) for specific gravity (SG) ≤1.015, or 2+ (100 mg/dL) for SG >1.015, or a random urine protein:creatinine ratio >0.2 (0.5 for age<2 years). Nephrotic syndrome (NS) has four components: (1) Nephrotic range proteinuria (>40 mg/m²/hour or >1,000 mg/m²/day); (2) edema; (3) hypoalbuminemia; and (4) hyperlipidemia.

Differential Diagnosis

• Transient proteinuria
  –With fever, dehydration, exercise, seizures, cold exposure, or stress
  –Rarely >2+ on dipstick
  –Usually remits within 1–2 weeks
• Orthostatic (postural) proteinuria
  –Occurs mostly in adolescence
  –First morning U/A is negative for protein

• Primary glomerular disease
  –MCNS: Most common cause of nephrotic syndrome (NS) in younger children, usually presents in ages 2–6, more common in boys; etiology possibly immune-mediated, typically responds to corticosteroids
  –Mesangial proliferative GN: Intermediate lesion between MCNS and FSGS
  –FSGS: Progressive disease of glomerular scarring, more common in blacks and adolescents, presents as NS or asymptomatic proteinuria, frequently resistant to corticosteroid therapy
  –Membranous nephropathy
  –Any primary GN (e.g., APSGN) can present with hematuria and proteinuria

• Systemic lupus erythematosus nephritis
• Henoch-Schönlein purpura (HSP)
• Wegener granulomatosis
• Tubulointerstitial disease: Proteinuria is less than with primary glomerular diseases
  –Reflux nephropathy
  –Renal dysplasia
  –Interstitial nephritis (especially NSAIDs)
  –Polycystic kidney disease
• Infectious disease
  –Bacterial (e.g., poststrep, shunt nephritis, leprosy, syphilis, infective endocarditis)
  –Viral (e.g., HBV, CMV, EBV, VZV, HIV)
  –Protozoal (e.g., malaria, toxoplasmosis)
  –Parasitic (e.g., schistosomiasis, filariasis)
• Neoplasm (e.g., lymphoma, leukemia, Wilms tumor, pheochromocytoma)
• Alport syndrome
• Fabry disease
• Nail-patella syndrome
• Medications (e.g. gold, mercurials)
• Constrictive pericarditis

Workup and Diagnosis

• History
  –Renal disease
  –Recurrent UTIs
  –HIV infection
  –Edema (periorbital or extremity)
  –Fatigue
  –Weight loss or gain
  –Pallor (seen with anemia of chronic disease)
  –Gross hematuria
  –“Foamy” urine
• Physical exam
  –Blood pressure, growth parameters
  –Edema (periorbital or extremity), ascites
  –Rashes or joint abnormalities
• Labs
  –Serum chemistries including albumin and triglycerides
  –U/A, 24-hour urine collection for protein
  –C3, C4
• If asymptomatic proteinuria, obtain “first morning” void, preferably prior to ambulation, to rule out orthostatic proteinuria before performing extensive lab workup
  –If U/A is negative for protein, additional diagnostic testing is not necessary
• Additional tests as indicated by the history
  –ANCA, ANA, HIV
• Renal ultrasound

Treatment

• All patients with persistent proteinuria should be referred to a pediatric nephrologist for evaluation
• Younger children with the typical presentation of MCNS are treated with an empiric course of corticosteroids (4–6 weeks of high dose followed by a gradual taper)
• Patients with atypical features (e.g., renal insufficiency, older age at presentation), asymptomatic proteinuria, or suspected systemic disease undergo renal biopsy with treatment directed at the underlying cause
• Patient with “steroid-dependent” or steroid-resistant forms of NS may be treated with alternative immunosuppressant agents (e.g., cyclosporine, mycophenolate)
• ACE inhibitors are an important adjunct therapy for proteinuric renal diseases, because they not only control hypertension if present, but also have direct antiproteinuric/antifibrotic effects

Book Source Details

• Book Title: In A Page: Pediatric Signs and Symptoms
• Author(s): Jonathan E. Teitelbaum, Kathleen O. Deantonis, Scott Kahan
• Year of Publication: 2007
• Copyright Details: In A Page: Pediatric Signs and Symptoms, Copyright © 2007 Lippincott Williams & Wilkins.

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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.

More About This Book: Title: In A Page: Pediatric Signs and Symptoms Authors: Jonathan E. Teitelbaum, Kathleen O. Deantonis, Scott Kahan Publisher: Lippincott Williams & Wilkins Copyright: 2007 ISBN: 1-4051-0427-9

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