Nephrotic syndrome happens when damage to your kidneys causes these organs to release too much protein into your urine.

Nephrotic syndrome isn’t itself a disease. Diseases that damage blood vessels in your kidneys cause this syndrome.

Nephrotic syndrome is characterized by the following:

  • a high amount of protein present in the urine (proteinuria)
  • high cholesterol and triglyceride levels in the blood (hyperlipidemia)
  • low levels of a protein called albumin in the blood (hypoalbuminemia)
  • swelling (edema), particularly in your ankles and feet, and around your eyes

In addition to the above symptoms, people with nephrotic syndrome may also experience:

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 your 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 your urine. Albumin helps pull extra fluid from your body into your kidneys. This fluid is then removed in your urine.

Without albumin, your body holds on to the extra fluid. This causes swelling (edema) in your legs, feet, ankles, and face.

Primary causes of nephrotic syndrome

Some conditions that cause nephrotic syndrome only affect the kidneys. These are called primary causes of nephrotic syndrome. These conditions include:

  • Focal segmental glomerulosclerosis (FSGS). This is 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. For a person with this disease, 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.

Secondary causes of nephrotic syndrome

Other diseases that cause nephrotic syndrome affect the whole body. These are called secondary causes of nephrotic syndrome. Such diseases can 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 your kidneys, possibly resulting in kidney damage.

Some medications, including infection-fighting drugs and nonsteroidal anti-inflammatory drugs (NSAIDs), have also been linked to nephrotic syndrome.

Diet is important for managing nephrotic syndrome. Limit the amount of salt you eat to prevent swelling and to manage 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. This can also help to reduce your risk of developing heart disease.

Although this condition causes you to lose protein in your urine, eating extra protein isn’t recommended. A high-protein diet can make nephrotic syndrome worse. Continue reading to learn more about the foods to eat and avoid when you have nephrotic syndrome.

Your doctor can treat the condition that caused nephrotic syndrome, as well as the symptoms of this syndrome. A variety of medications can be used to accomplish this:

  • Blood pressure medications. These can help to lower blood pressure and reduce the amount of protein lost in the urine. These medications include angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs).
  • Diuretics. Diuretics cause your kidneys to release extra fluid, which brings down swelling. These medications include things like furosemide (Lasix) and spironolactone (Aldactone).
  • Statins. These drugs lower cholesterol levels. Some examples of stains include atorvastatin calcium (Lipitor) and lovastatin (Altoprev, Mevacor).
  • Blood thinners. These medications reduce your blood’s ability to clot and may be prescribed if you’ve had a blood clot in your kidney. Examples include heparin and warfarin (Coumadin, Jantoven).
  • Immune system suppressants. These drugs help keep the immune system under control and can be helpful for treating an underlying condition like lupus. An example of an immune-suppressing medication is corticosteroids.

Your doctor may also want to take steps to reduce your risk of infection. To do this, they may recommend that you get a pneumococcal vaccine and yearly flu shot.

Both primary and secondary nephrotic syndrome can occur in children. Primary nephrotic syndrome is the most common type in children.

Some children can have something called congenital nephrotic syndrome, which happens in the first 3 months of life. This can be caused by an inherited genetic defect or an infection shortly after birth. Children with this condition may eventually need a kidney transplant.

In children, nephrotic syndrome causes these symptoms:

Kids with childhood nephrotic syndrome get more infections than usual. This is because the proteins that normally protect them from infection are lost in their urine. They may also have high blood cholesterol.

As in children, nephrotic syndrome in adults can have primary and secondary causes. In adults, the most common primary cause of nephrotic syndrome is focal segmental glomerulosclerosis (FSGS).

This condition is associated with a poorer outlook. The amount of protein present in the urine is a significant factor in determining prognosis in these individuals. About half of the people with FSGS and nephrotic syndrome progress to end-stage kidney disease in 5 to 10 years.

However, secondary causes of nephrotic syndrome also play an important role in adults. It’s estimated that over 50 percent of nephrotic syndrome cases in adults have a secondary cause such as diabetes or lupus.

To diagnose nephrotic syndrome, your doctor will first take your medical history. You’ll be asked about your symptoms, any medications you’re taking, and whether you have any underlying health conditions.

Your doctor will also perform a physical examination. This can include things like measuring your blood pressure and listening to your heart.

Several tests are used to help diagnose nephrotic syndrome. They include:

  • Urine tests. You’ll be asked to provide a sample of urine. This can be sent to a laboratory to determine whether you have high amounts of protein in your urine. In some cases, you may be asked to collect urine over a 24-hour period.
  • Blood tests. In these tests, a sample of blood will be taken from a vein in your arm. This sample can be analyzed to check blood markers of overall kidney function, blood levels of albumin, and cholesterol and triglyceride levels.
  • Ultrasound. An ultrasound uses sound waves to create an image of your kidneys. Your doctor can use the images created to evaluate the structure of your kidneys.
  • Biopsy. During a biopsy, a small sample of kidney tissue will be collected. This can be sent to a lab for further testing and can help to determine what may be causing your condition.

The loss of proteins from your blood as well as damage to the kidneys can lead to a variety of complications. Some examples of possible complications that someone with nephrotic syndrome may experience include:

  • Blood clots. Proteins that prevent clotting can be lost from the blood, raising your risk of blood clots.
  • High cholesterol and triglycerides. More cholesterol and triglycerides can be released into your blood. This can raise your risk of heart disease.
  • High blood pressure. Kidney damage can increase the amount of waste products in your blood. This can raise blood pressure.
  • Malnutrition. Loss of protein in the blood can lead to weight loss, which may be masked by swelling (edema).
  • Anemia. You have a lack of red blood cells to carry oxygen to the organs and tissues of your body.
  • Chronic kidney disease. Your kidneys may lose their function over time, necessitating dialysis or a kidney transplant.
  • Acute kidney failure. Kidney damage can cause your kidneys to stop filtering waste, which requires emergency intervention through dialysis.
  • Infections. People with nephrotic syndrome have an increased risk of getting infections, such as pneumonia and meningitis.
  • Underactive thyroid gland (hypothyroidism). Your thyroid doesn’t make enough thyroid hormone.
  • Coronary artery disease. Narrowing of blood vessels limits blood flow to the heart.

There are some things that can put you at an increased risk of developing nephrotic syndrome. These can include:

  • An underlying condition that can lead to kidney damage. Examples of such conditions include things like diabetes, lupus, or other kidney diseases.
  • Specific infections. There are some infections that may increase your risk of nephrotic syndrome, including HIV, hepatitis B and C, and malaria.
  • Medications. Some infection-fighting drugs and NSAIDs can increase the risk of nephrotic syndrome.

Remember that just because you have one of these risk factors doesn’t mean you’ll develop nephrotic syndrome. However, it’s important to monitor your health and see your doctor if you’re experiencing symptoms that are consistent with nephrotic syndrome.

The outlook for nephrotic syndrome can vary. It depends on what’s causing it to occur as well as your overall health.

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.

However, other conditions can eventually lead to kidney failure, even with treatment. When this happens, dialysis and possibly a kidney transplant will be required.

If you have symptoms that are troubling or you think that you may have nephrotic syndrome, make an appointment with your doctor to discuss your concerns.