Proteinuria is the presence of excess proteins in the urine. In healthy persons, urine contains very little protein; an excess is suggestive of illness. Excess protein in the urine often causes the urine to become foamy, although foamy urine may also be caused by bilirubin in the urine (bilirubinuria),[1] retrograde ejaculation, pneumaturia (air bubbles in the urine) due to a fistula,[2] or drugs such as pyridium.[1]


There are three main mechanisms to cause proteinuria:

Proteinuria can also be caused by certain biological agents, such as bevacizumab (Avastin) used in cancer treatment. Excessive fluid intake (drinking in excess of 4 litres of water per day) is another cause.[3][4]

Also leptin administration to normotensive Sprague Dawley rats during pregnancy significantly increases urinary protein excretion.[5]

Proteinuria may be a sign of renal (kidney) damage. Since serum proteins are readily reabsorbed from urine, the presence of excess protein indicates either an insufficiency of absorption or impaired filtration. People with diabetes may have damaged nephrons and develop proteinuria. The most common cause of proteinuria is diabetes, and in any person with proteinuria and diabetes, the cause of the underlying proteinuria should be separated into two categories: diabetic proteinuria versus the field.

With severe proteinuria, general hypoproteinemia can develop which results in diminished oncotic pressure. Symptoms of diminished oncotic pressure may include ascites, edema and hydrothorax.

Conditions with proteinuria as a sign

Proteinuria may be a feature of the following conditions:[6]

Conditions with proteinuria consisting mainly of Bence-Jones proteins as a sign

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