Nephrotic syndrome is not a disease; it is rather a designation for a whole group of symptoms that sometimes occur in kidney diseases. We should not confuse it with nephritic syndrome that has similar name but quite different symptoms.
The essence of nephrotic syndrome is a large protein loss in urine. The syndrome is defined as the loss of more than 3 grams of proteins into urine per 24 hours. Normally, protein in urine is virtually absent, but diseases associated with the nephrotic syndrome (see below), cause disruption of kidneys’ filtering ability and increase the penetration of protein molecules into the urine.
Nephrotic syndrome typically accompanies certain types of glomerulonephritis. Glomerulonephritides are specific inflammatory diseases of the kidneys that are related to abnormal function of the immune system. In addition, the nephrotic syndrome occurs in systemic diseases such as diabetes (where it is a form of diabetic nephropathy) and lupus erythematosus.
Lack of protein causes swelling, which is best visible around the eyes and in the lower extremities. The mechanism of edema is caused by decreased oncotic pressure within the blood vessels, which is maintained by proteins and which helps to keep the fluid within. Without the proteins, the fluids may filter through the blood vessels’ walls into surrounding tissue.
People with nephrotic syndrome suffer from weakened immunity, because they lose protective antibodies to urine (antibodies are also proteins).
The syndrome also includes high cholesterol and increased risk of atherosclerosis and its complications. The accurate explanation of the increased cholesterol serum level is somewhat difficult for the layman, so let us be content with the statement that when the body loses protein in the urine, it increases formation of cholesterol molecules.
The protein loss and the disorders of blood fluid management cause disruption of internal environment and affect the blood clotting. The situation results in thrombophilic state with increased risk of formation of blood clots including higher occurrence of deep vein thrombosis of the lower extremities and subsequent pulmonary embolism.
The patient suffers from the above described swelling and blood tests show increased level of cholesterol. Urinalysis is essential as it can confirm the presence of protein in the urine. The syndrome must be confirmed by collecting urine for 24 hours and determination of the daily protein loss from a sample of this urine. When the daily protein loss is higher than three grams, the diagnosis is confirmed. Patient with nephrotic syndrome should have his kidneys thoroughly tested.
It is necessary to note, however, that in addition to the diagnosis, it is also necessary to look for its cause. The patient should be examined by a nephrologist and when there is a suspicion of a glomerulonephritis, the kidney biopsy may be indicated to obtain a sample of tissue for further examination.
The main therapeutic approach should focus on treatment of the underlying cause, if possible. The symptomatic supportive treatment includes higher intake of high quality proteins and administration of drugs lowering the high cholesterol.