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Proteinuria

Last updated: January 2, 2020

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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 [1]

Urinalysis

Proteinuria can cause foamy urine!

Diagnosis of underlying disease

References:[1][2]

According to quantity

Microalbuminuria

Overt proteinuria (formerly "macroalbuminuria")

According to origin

Glomerular proteinuria

Tubular proteinuria

Mixed proteinuria

Found in diseases that affect both the glomeruli and the tubules (e.g., chronic renal failure)

Prerenal proteinuria (or overflow proteinuria)

Postrenal proteinuria

References:[1][3][4][5][6]

  • 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

References:[1]

  1. Rovin BH. Assessment of urinary protein excretion and evaluation of isolated non-nephrotic proteinuria in adults. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/assessment-of-urinary-protein-excretion-and-evaluation-of-isolated-non-nephrotic-proteinuria-in-adults.Last updated: January 25, 2017. Accessed: April 20, 2017.
  2. Goldman L, Schafer AI. Goldman-Cecil Medicine, 25th Edition. Elsevier ; 2016
  3. Kumar V, Abbas AK, Aster JC. Robbins & Cotran Pathologic Basis of Disease. Elsevier Saunders ; 2014
  4. Devkota BP, Staros EB. Microalbumin. Microalbumin. New York, NY: WebMD. http://emedicine.medscape.com/article/2088184. Updated: January 17, 2014. Accessed: August 20, 2017.
  5. Kher K, Schnaper HW, Makker SP. Clinical Pediatric Nephrology. CRC Press ; 2006
  6. Swaminathan R. Handbook of Clinical Biochemistry. World Scientific ; 2011
  7. Herold G. Internal Medicine. Herold G ; 2014
  8. 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