Nephrotic syndrome happens when damage to your kidneys causes them to release too much protein into your urine. Other characteristics of this disease include:
- swelling in your legs, ankles, feet, and face
- high cholesterol levels
- high triglyceride levels
Nephrotic syndrome isn’t itself a disease. Diseases that damage blood vessels in your kidneys cause this condition.
Symptoms of nephrotic syndrome
Symptoms of nephrotic syndrome include:
- swelling (edema) in your ankles and feet, and around your eyes
- foamy urine
- weight gain from fluid buildup in your body
- appetite loss
- high cholesterol and triglyceride levels
Causes of nephrotic syndrome
Your kidneys are filled with tiny blood vessels, called glomeruli. As your blood moves through these vessels, extra water and waste products are filtered into the urine. Protein and other substances that your body needs stay in your bloodstream.
Nephrotic syndrome happens when the glomeruli are damaged and can’t properly filter your blood. Damage to these blood vessels allows protein to leak into your urine.
Albumin is one of the proteins lost in the urine. Albumin helps pull extra fluid from your body into your kidneys. This fluid is then removed in the urine. Without albumin, your body holds onto the extra fluid. This causes swelling (edema) in your legs, feet, ankles, and face.
Some conditions that cause nephrotic syndrome only affect the kidneys. These are called primary causes of nephrotic syndrome. These conditions include:
- Focal segmental glomerulosclerosis. A condition in which the glomeruli become scarred from disease, a genetic defect, or an unknown cause.
- Membranous nephropathy. In this disease, the membranes in the glomeruli thicken. The cause of the thickening isn’t known, but it may occur along with lupus, hepatitis B, malaria, or cancer.
- Minimal change disease. In this condition, the kidney tissue looks normal under a microscope, but for some unknown reason, it doesn’t filter properly.
- Renal vein thrombosis. In this disorder, a blood clot blocks a vein that drains blood out of the kidney.
Other diseases that cause nephrotic syndrome affect the whole body. These are called secondary causes of nephrotic syndrome. These conditions include:
- Diabetes. In this disease, uncontrolled blood sugar can damage blood vessels all over your body, including in your kidneys.
- Lupus. Lupus is an autoimmune disease that causes inflammation in the joints, kidneys, and other organs.
- Amyloidosis. This rare disease is caused by a buildup of the protein amyloid in your organs. Amyloid can build up in, and damage your kidneys.
Some medications, including antibiotics and nonsteroidal anti-inflammatory drugs (NSAIDs), have also been linked to nephrotic syndrome.
How is it treated?
Your doctor can treat the condition that caused nephrotic syndrome, as well as the symptoms of this syndrome.
Blood pressure medications lower blood pressure, and reduce the amount of protein lost in the urine. These medications include:
- angiotensin-converting enzyme inhibitors — benazepril (Lotensin), captopril (Capoten), and enalapril (Vasotec)
- angiotensin II receptor blockers — losartan potassium (Cozaar) and valsartan (Diovan)
Diuretics cause your kidneys to release extra fluid, which brings down swelling. These medications include:
- furosemide (Lasix)
- spironolactone (Aldactone)
Statins lower cholesterol levels. These medications include:
- atorvastatin calcium (Lipitor)
- fluvastatin sodium (Lescol)
- lovastatin (Altoprev, Mevacor)
- pravastatin sodium (Pravachol)
- rosuvastatin calcium (Crestor)
- simvastatin (Zocor)
Because of the increased risk for infection, your doctor may recommend that you get a pneumococcal vaccine and yearly flu shot.
Diet is also important for controlling nephrotic syndrome. Limit the amount of salt you eat to prevent swelling and to control your blood pressure. Your doctor may also suggest that you drink less fluid to reduce swelling.
Nephrotic syndrome can increase your cholesterol and triglyceride levels, so try to eat a diet that’s low in saturated fat and cholesterol.
Although this condition causes you to lose protein in your urine, eating extra protein is not recommended. A high-protein diet can make nephrotic syndrome worse.
Complications and related conditions
Damage to the kidneys from nephrotic syndrome can lead to these complications:
- blood clots
- high cholesterol and triglycerides
- high blood pressure
- a lack of red blood cells to carry oxygen to your body (anemia)
- chronic kidney disease
- acute kidney failure
- increased risk of infections such as pneumonia and meningitis
- underactive thyroid gland (hypothyroidism)
- coronary artery disease
How does it affect children?
Children can also get nephrotic syndrome. Just as in adults, there are two types of nephrotic syndrome that affect children:
- Primary nephrotic syndrome. This condition only affects the kidneys and is the most common type in children.
- Secondary nephrotic syndrome. This condition is caused by other diseases, such as diabetes or lupus.
In children, nephrotic syndrome causes these symptoms:
- fever, fatigue, irritability, and other signs of infection
- loss of appetite
- blood in the urine
- high blood pressure
Kids with childhood nephrotic syndrome get more infections than usual. This is because the proteins that normally protect them from infection are lost in the urine. They may also have high blood cholesterol.
Treatments for childhood nephrotic syndrome include:
- corticosteroids or other medications that reduce the immune system response
- diuretics to remove extra fluid from the body
- blood pressure-lowering medications such as angiotensin receptor blockers or angiotensin-converting enzyme inhibitors
- medications to treat the cause of nephrotic syndrome, such as diabetes or lupus
Children who are born with nephrotic syndrome (congenital nephrotic syndrome), may eventually need a kidney transplant.
Some of the diseases that cause nephrotic syndrome get better on their own or with treatment. Once the underlying disease has been treated, nephrotic syndrome should improve. Other conditions can eventually lead to kidney failure, even with treatment.