Proteinuria
Proteinuria was found in 5-Minute Clinical Consult which helps you diagnose, treat, and follow up on over 900 medical conditions seen in everyday practice.

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Basics

Description

Urinary protein excretion of >150 mg/d:

  • Nephrotic-range proteinuria: Urinary protein excretion of >3.5 g/d; also called heavy proteinuria
Pediatric Considerations
  • Proteinuria: Normal is daily excretion of up to 100 mg/m2 (body surface area)
  • Nephrotic-range proteinuria: Daily excretion of >1,000 mg/m2 (body surface area)
  • 3 pathologic types:
    • Glomerular proteinuria: Increased permeability of proteins across glomerular capillary membrane
    • Tubular proteinuria: Decreased proximal tubular reabsorption of proteins
    • Overflow proteinuria: Increased production of low-molecular-weight proteins
Pregnancy Considerations
  • Proteinuria in pregnancy beyond 20 weeks' gestation is a hallmark of pre-eclampsia/eclampsia and demands further workup.
  • Proteinuria in pregnancy before 20 weeks' gestation is suggestive of underlying renal disease.

Risk Factors

  • Hypertension
  • Diabetes
  • Obesity
  • Excessive exercise
  • Congestive heart failure (CHF)
  • UTI
  • Fever

Genetics
No known genetic pattern

General Prevention

Control of weight, BP, and blood glucose reduces the risk of proteinuria.

Pathophysiology

  • Glomerular proteinuria: Increased filtration/larger proteins (albumin) due to:
    • Increased size of glomerular basement membrane pores and
    • Loss of proteoglycan negative charge barrier
  • Tubular proteinuria: Tubulointerstitial disease prevents proximal tubular reabsorption of smaller proteins (β2-microglobulin, immunoglobulin (Ig) light chains, retinol-binding protein, amino acids).
  • Overflow proteinuria: Proximal tubular reabsorption overwhelmed by increased production of smaller proteins

Etiology

  • Glomerular proteinuria:
    • Primary glomerulonephropathy:
      • Minimal-change disease
      • Idiopathic membranous glomerulonephritis
      • Focal segmental glomerulonephritis
      • Membranoproliferative glomerulonephritis
      • IgA nephropathy
    • Secondary glomerulonephropathy:
      • Diabetic nephropathy
      • Autoimmune/collagen-vascular disorders (e.g., lupus nephritis, Goodpasture syndrome)
      • Amyloidosis
      • Preeclampsia
      • Infection (HIV, hepatitis B and C, poststreptococcal, endocarditis, syphilis, malaria)
      • Malignancy (GI, lung, lymphoma)
      • Renal transplant rejection
      • Structural (reflux nephropathy, polycystic kidney disease)
      • Drug-induced (NSAIDs, penicillamine, lithium, heavy metals, gold, heroin)
  • Tubular proteinuria:
    • Hypertensive nephrosclerosis
    • Tubulointerstitial disease (uric acid nephropathy, hypersensitivity, interstitial nephritis, Fanconi syndrome, heavy metals, sickle-cell disease, NSAIDs, antibiotics)
    • Acute tubular necrosis
  • Overflow proteinuria:
    • Multiple myeloma (light chains; also tubulotoxic)
    • Hemoglobinuria
    • Myoglobinuria (in rhabdomyolysis)
    • Lysozyme (in acute monocytic leukemia)
  • Benign proteinuria:
    • Functional (fever, exercise, cold exposure, stress, CHF)
    • Idiopathic transient
    • Orthostasis (postural)

Commonly Associated Conditions

  • Hypertension (common)
  • Diabetes mellitus (common)
  • Preeclampsia (common)
  • Multiple myeloma (rare)

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