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When the kidneys are healthy and functioning properly, filtering fluids, minerals and waste products from the blood, they usually do not allow large amounts of serum protein to be isolated in the urine. But when the kidneys do not filter properly, proteinuria can occur, which means that an unusual amount of protein is present in the urine.

The two main groups of serum proteins in the blood are albumin and globulins. Albumin is abundant in the blood, making up more than 50% of all serum proteins. Its functions include maintaining the right amount of water in the bloodstream, as well as binding and transporting substances that are poorly soluble in water – fat-soluble vitamins, calcium and some medicaments.

Transient proteinuria is a temporary release of protein and can be the result of strenuous exercise, fever, exposure to cold, stress and other conditions. Pregnant women can also excrete more protein in their urine. Transient proteinuria does not involve underlying kidney disease and does not require treatment.

Proteinuria might be also due to kidney disease, such as glomerulonephritis, primary focal segmental glomerulosclerosis (FSGS), or kidney damage due to systemic disease. Microalbuminuria means that low levels of albumin are found in the urine. Microalbuminuria may indicate that people with diabetes or hypertension develop an early stage of kidney disease.

Symptoms of proteinuria

In most cases, proteinuria has no symptoms and is detected during routine screening in people with high blood pressure or diabetes. If the protein loss is severe, swelling or edema may occur. Swelling may be present in:

  • The face and around the eyes
  • Hands and feet
  • Ankles and feet
  • Abdomen


There are three types of kidney damage (insufficiency) – prerenal, renal and postrenal. The mechanisms of occurrence are radically different, as in some cases the cause lies in the kidneys, and in others they are secondarily affected.

Prerenal acute impairment occurs when a sudden decrease in blood flow to the kidneys (renal hypoperfusion) causes loss of renal function. In these cases, the kidney structures are preserved and healthy but low blood pressure leads to a collapse of their function, stops the filtration of blood and urine production.

In renal damage, the renal glomeruli and especially the tubules (tubules) are affected by a real disease process. Treatment includes identifying and correcting the cause of the kidney damage. This often involves nephrotoxic drugs, glomerulonephritis, lupus, rhabdomyolysis and other specific kidney diseases. As a result of impaired blood supply through the renal arteries, secondary organic damage can occur, which can lead not only to a sudden loss of renal function, but also to remain even after the restoration of blood flow.

Postrenal renal failure is due to obstruction (blockage) of the urinary tract at various levels and causes the accumulation of waste in the kidneys. Obstruction of the urinary tract can lead to accumulation of urine in one or both kidneys. Over time, this accumulation of fluid can interfere with the normal flow of urine from the kidneys. This is usually a reversible process if the obstacle is removed. However, there are cases in which prolonged urinary tract infections can lead to permanent and severe damage to the renal parenchyma.