Nephrotic syndrome is a nonspecific disorder in which the kidneys are damaged, causing them to leak large amounts of protein from the blood into the urine. Nephrotic syndrome can be triggered by various disorders which damage the kidneys, particularly the basement membrane of the glomerulus, and when the basement membrane is damaged, there is abnormal excretion of protein in the urine. The most common cause of nephrotic syndrome in children is minimal change disease, and in adults the main cause is membranous glomerulonephritis.
Kidneys affected by nephrotic syndrome have small pores in the podocytes, large enough to permit proteinuria (and subsequently hypoalbuminemia, because some of the protein albumin has gone from the blood to the urine) but not large enough to allow cells through (hence no hematuria). By contrast, in nephritic syndrome, RBCs pass through the pores, causing hematuria.
Nephrotic syndrome also occurs as a result of infection, such as strep throat, hepatitis, or mononucleosis, use of certain drugs, cancer, genetic disorders, immune disorders, or diseases that affect multiple body systems including diabetes, systemic lupus erythematosus, multiple myeloma, and amyloidosis. swelling is the most common symptom, specially in the feet and ankles. Other symptons are weight gain from fluid retention, foamy appearance of the urine, high blood pressure, poor appetite.