Nephrotic syndrome (also called nephrosis) happens when your kidneys start losing large amounts of protein in your urine. As your kidneys get worse, extra fluids and salt build up in your body. This causes you to have swelling (edema), high blood pressure and higher levels of cholesterol.

Why do patients with nephrotic syndrome have edema?

In nephrotic syndrome, a defective glomerular filtration barrier allows the passage of proteolytic enzymes or their precursors, which have the ability to activate the epithelial sodium channel, thereby causing the the subsequent sodium retention and oedema.

Why does kidney disease cause water retention?

Kidney disease or kidney damage

Damage to the glomeruli, which are the capillaries in the kidneys that filter waste and excess fluids from the blood, can result in nephrotic syndrome. One symptom of this is a low level of the protein albumin in the blood. This can lead to edema.