Proteinuria Definition

What is proteinuria?

Under proteinuria refers to the excessive excretion of proteins in the urine. The limit for a normal (physiological) protein excretion is set at less than 150 milligrams per day. An increased protein excretion may be a harmless, temporary event and is then referred to as benign reversible proteinuria. However, persistently elevated levels of protein in the urine are not only the result of various diseases, but also an important independent cause of the progression of renal disease.


An important function of the kidneys is to filter blood plasma, this is done in the Glomeruli of the renal Corpuscle. Proteins from a molecular weight of 80 Kilodalton (kDa) - for example, globulin - are held back by this "filter". However, substances pass through this barrier up to a molecular weight of 6-15 kDa. In addition to this size selectivity, there is also a charge selectivity, that is holding back strongly negatively charged proteins.

Albumin with its molecular weight of 66-69 kDa is retained to 99.97. The solute sieving coefficient for albumin is thus, 0,001. reason is the strong negative charge of the albumin molecule that prevents a greater filtration. The Glomerular filter is permeable for equal-sized molecules with missing or even positive charge.

Into the primary urine proteins are classified into macro - and micro-molecular proteins, draw the line in the albumin and its molecular mass. These proteins are re absorbed in the proximal renal tubule to 96 percent. The recording via the mediation of receptors of Megalin-Cubilin complex as a specific, ATP-dependent Endocytosis. Small amounts of protein in the urine of the end appears so also under physiological conditions.


The causes of a pathological proteinuria are changes coming to fruition at the actual formation of urine or have nothing to do with this. The former to be the latter in pre-renal renal Glomerular and tubular Proteinurien forms, (or präglomeruläre) and divided forms of post renal.

The prärenal remote causes lead to oversupply of proteins and to a so-called Überlaufproteinurie. With these pathologically elevated concentrations (low molecular weight) protein in the serum, there consequently to an increased filtration and exceeding the capacity of absorption of these proteins in the proximal tubule of the nephron.

A disturbance localized in the Glomerulum - usually it is an inflammation (Glomerulonephritis) - causes a durchlässigeren filter so that the absorption capacity in the renal tubule is exceeded as well.

Troubleshooting the Tubuluszellfunktion, the re-absorption of proteins is primarily affected. Normal levels of protein in the urine of primary lead to a significant proteinuria.

For postrenalen errors, the proteins come from the urinary tract derived from.

When a protein excretion in the urine of more than 3-3.5 g per 24 hours, when children of more than 1 g per m ² surface and 24 hours, a so-called great proteinuria spoken by. This usually resulted in the emergence of nephrotic syndrome.


The reason for the emergence of a large proteinuria are:

-Acute and chronic glomerulonephritis
-Metabolic disease such as diabetes mellitus
-System diseases such as amyloidosis, systemic lupus erythematosus, inter alia,
-Cardiac and vascular causes, particularly arterial hypertension
-Hematologic diseases such as sickle cell anemia
-Congenital disorders such as congenital nephrotic syndrome or Alport syndrome
-Complications of pregnancy such as preeclampsia
-A kidney transplant
-Chronic transplant rejection
-Microorganisms, viruses


In addition to the amount, the composition of proteins of importance is. So a disease can occur even in minor proteinuria if there is a pathological pattern of distribution. This is true of arterial hypertension or a Lupus especially for systemic diseases such as diabetes mellitus, Erythematosus.

Of 500 in the urine of healthy individuals existing proteins, much is still not identified, where sensitive measuring methods such as Radioimmunoassay or Nephelometry remedy.

The major urinary proteins are

-Globulins (Alpha-1 micro globulins and macro alpha-2 globulins),
-Uromodulin (Tamm-Horsfall protein), the quantitatively most important physiological protein formed in the kidney,.
-Antibody light chain (Kappa - and lambda light chains).

Albumin can be excreted increased as a lack of tubular reabsorption also in disorders of glomerular filtration. A clinically isolated albumin excretion as albuminuria, but the designated common Harnstreifen undetectable at a diabetes clinically meaningful slight albuminuria as microalbuminuria.

Medical importance

People in whom an increased excretion of albumin is detected in urine, have an increased risk of suffering later in a progressive loss of kidney function and even kidney failure requiring dialysis. For a given renal function increases with increasing proteinuria, the mortality and the risk of suffering a heart attack

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