What is proteinuria?

Updated: Mar 25, 2020
  • Author: Beje Thomas, MD; Chief Editor: Vecihi Batuman, MD, FASN  more...
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The detection of proteins excreted in the urine has been extensively used in the assessment of renal diseases. Proteinuria  identifies patients with renal damage and those at risk for worsening renal disease and increased cardiovascular morbidity.  An individual with proteinuria in the setting of a normal glomerular filtration rate (GFR) is at high risk of progressive loss of renal function.  The 2012 Kidney Disease: Improving Global Outcomes (KDIGO) clinical practice guideline for the evaluation and management of chronic kidney disease (CKD) includes proteinuria in the staging of CKD. It is important to note when proteinuria is present and can be reduced, as lowering proteinuria has a protective effect against further loss of kidney function.

Normal urinary protein excretion is 30 mg/day considered abnormal. AER between 30 to 300 mg/day is called moderately increased albuminuria. Levels greater than 300 mg/day are called severely increased albuminuria. In the past, moderately and severely increased albuminuria were referred to as microalbuminuria and macroalbuminuria, respectively.  Albuminuria that persists for 3 months is considered CKD. Nephrotic range proteinuria is defined as greater than 3.5 g of protein excreted in the urine over 24 hours. [1, 2]

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