Kidneys receive approximately 1 liter of blood every minute. Of this, about 100 ml gets filtered in the kidney. This contains, small molecules and few large molecules. This is due to the intricate cellular structure that prevents proteins from getting filtered into the urinary space. A derangement of this filter results in passage of heavy amounts of proteins in urine. This condition is called heavy proteinuria or Nephrotic syndrome or Nephrosis.
In the urine, the protein excretion is > 3.5 gm/day or in children, it is >50mg/kg of body weight. In most cases, the serum albumin is <3gm/dl (normal>4), and passage of lipids in the urine. The lipids in the blood increase and swelling of face and feet also occur.
Causes of Nephrotic Syndrome:
In children, most cases are due to Minimal Change Disease, FSGS, MPGN etc. In adults, most cases are due to primary illness while upto 30% may be due to secondary illness.
Apart from edema, there is a tendency towards clotting of the blood in blood vessels. If this involves a critical area, like heart, brain or kidneys complications may occur. Infections also are common. In addition, kidney function may be reduced due to either the disease or its treatment. Sometime the blood pressure may be elevated.
In some cases, continuation of excess proteins in the urine may lead to glomerular damage and Chronic kidney disease leading to renal failure.
After confirmation of excess protein in the urine, a kidney biopsy is required in most cases. In children between 2 to 8 years, a biopsy may be deferred if there is a good response to steroids as Minimal Change disease is presumed.
The treatment consists of steroids in primary cases and in case of poor response other immunosuppressants and ACE-Inhibitors. Disease often has remissions and relapses which need to be monitored and treated appropriately.