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Proteinuria

Last updated: March 17, 2021

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Proteinuria is defined as a urinary protein excretion of > 150 mg/day. It has many possible causes, which may be benign (e.g., fever, intense exercise, dehydration) or more serious (e.g., glomerulonephritis, multiple myeloma). There are three different pathophysiological mechanisms that may lead to proteinuria: damage to the glomeruli (glomerular), damage to the tubules (tubular), or overproduction of low-molecular-weight proteins (overflow). If proteinuria is detected, patients should be further evaluated (e.g., additional urinalyses) to determine the underlying cause. The detection of microalbuminuria is of particular importance, as it suggests early diabetic or hypertensive nephropathy.

Proteinuria = urinary protein excretion of > 150 mg/day

Urinalysis

Proteinuria can cause foamy urine.

Diagnosis of underlying disease

References:[1]

According to quantity

Microalbuminuria

Overt proteinuria (formerly "macroalbuminuria")

According to origin

Glomerular proteinuria [2][3]

Tubular proteinuria

Mixed proteinuria

Prerenal proteinuria (or overflow proteinuria)

Postrenal proteinuria

  • Defined as isolated proteinuria < 3.5 g/day
  • Important, benign differential diagnosis in the evaluation of proteinuria
  • Very common; mostly affects younger individuals
  • Types of benign proteinuria
    • Orthostatic proteinuria (postural proteinuria): increased protein excretion only in the upright position
    • Transient proteinuria
      • Most common cause of isolated proteinuria in children
      • Causes:
        • Heavy exertion/stress
        • Fever
        • Seizures
        • Exposure to cold temperatures
    • Women can present with mild proteinuria due to vaginal discharge.
  • A dipstick test should be repeated to exclude underlying disease.
  • No treatment necessary; excellent prognosis
  1. Goldman L, Schafer AI. Goldman-Cecil Medicine, 25th Edition. Elsevier ; 2016
  2. Kher K, Schnaper HW, Makker SP. Clinical Pediatric Nephrology. CRC Press ; 2006
  3. Swaminathan R. Handbook of Clinical Biochemistry. World Scientific ; 2011
  4. Herold G. Internal Medicine. Herold G ; 2014
  5. Longo D, Fauci A, Kasper D, Hauser S, Jameson J, Loscalzo J. Harrisons's Principles of Internal Medicine, 18th Edition, 2011. McGraw-Hill Medical ; 2011