What is edema?
Patients with kidney disease experience edema due to either a heavy loss of protein in the urine or impaired kidney (renal) function.
Heavy loss of protein in the urine
Generally, nephrotic syndrome results from damage to the kidneys’ glomeruli—the tiny blood vessels that filter waste and excess water from the blood and send them to the bladder as urine. Glomeruli keep protein in the body. When they are damaged, protein leaks into the urine. Healthy kidneys allow less than one gram of protein to spill into the urine in a day.
In nephrotic syndrome, the glomeruli allow three grams or more of protein to leak into the urine during a 24-hour period. Nephrotic syndrome may occur with many diseases, including the kidney diseases caused by type 2 diabetes. What causes nephrotic syndrome is not always known.