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 this symptom may also be caused by other conditions). Severe proteinuria can cause nephrotic syndrome in which there is worsening swelling of the body. Signs and symptoms
Proteinuria often causes no symptoms and it may only be discovered incidentally.Foamy urine is considered a cardinal sign of proteinuria, but only a third of people with foamy urine have proteinuria as the underlying cause. It may also be caused by bilirubin in the urine (bilirubinuria), retrograde ejaculation, pneumaturia (air bubbles in the urine) due to a fistula, or drugs such as pyridium. Causes
There are three main mechanisms to cause proteinuria:
Due to disease in the glomerulus
Because of increased quantity of proteins in serum  (overflow proteinuria)
Due to low reabsorption at proximal tubule (Fanconi syndrome)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.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.
In patients whose proteinuria is not controlled with ACE inhibitors, the addition of an aldosterone antagonist (i.e., spironolactone) or angiotensin receptor blocker (ARB) may further reduce protein loss. Caution must be used if these agents are added to ACE inhibitor therapy due to the risk of hyperkalemia. Proteinuria secondary to autoimmune disease should be treated with steroids or steroid-sparing agent plus the use of ACE inhibitors. See also
Albuminuria
Microalbuminuria
List of terms associated with diabetes
Protein toxicity
Major urinary proteins
UPCR

References


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