What is Nephrotic syndrome?
Nephrotic syndrome is a condition marked by very high levels of protein in the urine (proteinuria); low levels of protein in the blood; swelling, especially around the eyes, feet, and hands; and high cholesterol. Nephrotic syndrome results from damage to the kidneys' glomeruli, which are tiny blood vessels that filter waste and excess water from the blood and send them to the bladder as urine. Nephrotic syndrome can occur with many diseases, including the kidney diseases caused by diabetes mellitus, but some causes are unknown.
Nephrotic syndrome can affect all age groups. In children, it is most common from the age of 2 to 6 years. Males are slightly more likely to be affected than females.
What is the cause?
Nephrotic syndrome is caused by various disorders that damage the kidneys, particularly the basement membrane of the glomerulus. This immediately causes abnormal excretion of protein in the urine. The most common cause in children is minimal change disease, while membranous glomerulonephritis is the most common cause in adults.
This condition can also occur as a result of infection, drug exposure, malignancy, hereditary disorders, immune disorders, or diseases that affect multiple body systems including diabetes, systemic lupus erythematosus, multiple myeloma, and amyloidosis. It can accompany kidney disorders, including glomerulonephritis, focal and segmental glomerulosclerosis, and mesangiocapillary glomerulonephritis.
What are the symptoms?
- Swelling (oedema): general, around the eyes, in the extremities, especially the feet and ankles
- Swollen abdomen
- Facial swelling
- Foamy appearance of the urine
- Weight gain (unintentional) from fluid retention
- Poor appetite
- High blood pressure
How is it diagnosed?
Physical examination can detect some symptoms. Other symptoms and signs of causative disorders can also be found with examination. Urinalysis reveals large amounts of urine protein. Fats are often also present in the urine. Tests to rule out various causes may include the following:
- Glucose tolerance test
- Antinuclear antibody
- Rheumatoid factor
- Complement levels
- Hepatitis B and C antibodies
- VDRL serology
- Serum protein electrophoresis
- Kidney biopsy
Nephrotic syndrome can also alter the results of the following tests:
- Urinary casts
- Protein electrophoresis - urine
- Serum iron
What is the treatment?
The goals of treatment are to relieve symptoms, prevent complications and delay progressive kidney damage. Treatment of the causative disorder is necessary to control nephrotic syndrome. Corticosteroid, immunosuppressive, antihypertensive, and diuretic medications may help control symptoms. Antibiotics may be needed to control infections. Angiotensin converting enzyme (ACE) inhibitors may significantly reduce the degree of protein loss in the urine and are therefore frequently prescribed for treatment of nephrotic syndrome.
If hypertension occurs, it must be treated vigorously. Treatment of high blood cholesterol and triglyceride levels is also recommended to reduce the risk of atherosclerosis. Dietary limitation of cholesterol and saturated fats may be of little benefit, as the high levels which accompany this condition seem to be the result of overproduction by the liver rather than from excessive fat intake. Medications to reduce cholesterol and triglycerides may be recommended. In many patients, reducing the amount of protein in the diet produces a decrease in urine protein. In most cases, a moderate-protein diet is usually recommended. Sodium (salt) may be restricted to help control swelling. Vitamin D may need to be replaced if nephrotic syndrome is chronic and unresponsive to therapy.
Nephrotic syndrome may go away once the underlying cause, if known, has been treated. In children, 80 percent of cases of nephrotic syndrome are caused by minimal change disease, which can be successfully treated with prednisone. However, in adults, most of the time the underlying cause is a kidney disease such as membranous nephropathy or focal segmental glomerulonephritis, and these diseases often persist even with treatment. In these cases, the kidneys may gradually lose their ability to filter wastes and excess water from the blood. If kidney failure occurs, the patient will need dialysis or a kidney transplant.
What is the prognosis?
The outcome varies; the syndrome may be acute and short-term or chronic and unresponsive to therapy. The cause and development of complications also affects the outcome.
What are the complications?
- Atherosclerosis and related heart diseases
- Renal vein thrombosis
- Chronic and acute renal failure
- Infections, including pneumococcal pneumonia
- Fluid overload, congestive heart failure, pulmonary oedema
Can it be prevented?
Treatment of causative disorders may prevent the development of nephrotic syndrome.