What Is Nephrotic Syndrome?
Nephrotic syndrome isn’t a disease. It’s a group of symptoms that can appear if your kidneys aren’t working right.
Small blood vessels in your kidneys function as a filter, clearing out waste and extra water from your blood. That waste and water ends up in your bladder and leaves your body as urine. These vessels are part of what’s called “glomeruli,” the filtering part of your kidney.
When they’re damaged, too much protein slips through the filters into your urine. The result is nephrotic syndrome.
Nephrotic syndrome can affect both adults and children. It is treatable.
Nephrotic Syndrome Causes
You might have a condition that affects only your kidneys. Doctors call that a “primary” cause of nephrotic syndrome.
Or you might have an issue with another part of your body that also affects your kidneys. That’s called a “secondary” cause of nephrotic syndrome.
Some of the conditions that can damage your glomeruli include:
Minimal change disease. Minimal change disease is the main cause of nephrotic syndrome in children. Kidney tissue from people with this disease looks relatively normal under a microscope. Doctors don’t know why this disease stops the kidneys from working properly. Some potential causes of the disease include infections from viruses, allergic reactions, taking certain medications, and using nonsteroidal anti-inflammatory drugs (NSAIDs).
Focal segmental glomerulosclerosis (FSGS). Focal segmental glomerulosclerosis is a disease that scars the glomeruli. It’s the most common primary cause of nephrotic syndrome in adults. FSGS can also be caused by a virus (such as HIV), medications, genetic mutations, obesity, high blood pressure, vascular disease, and many other things.
Membranous nephropathy. This condition causes the membranes of the glomeruli to thicken. PLA2R antibodies cause the majority of primary membranous nephropathies. Secondary causes include cancer, malaria, hepatitis B, and lupus.
Diabetes . Diabetes is the most common secondary cause of nephrotic syndrome in adults. It can cause kidney damage, known as diabetic nephropathy.
Lupus. Lupus is a chronic disease of the immune system, can seriously damage the kidneys.
Amyloidosis. Amyloidosis happens when you have a buildup of substances called amyloid proteins in your blood. This can damage your kidneys.
Nephrotic Syndrome Symptoms
There are four main symptoms of nephrotic syndrome. They are:
Proteinuria
This means you have too much protein in your urine. Nephrotic syndrome damages the filters, called glomeruli, that remove waste from your blood. Normally these filters keep protein in your body because your body needs it to work properly. Damaged filters allow protein to leak into your urine.
Hyperlipidemia
This means you have high fat and cholesterol levels in your blood. Nephrotic syndrome causes hyperlipidemia by increasing the amount of fat and cholesterol produced in your liver and by slowing the rate at which your body removes these fatty substances. Having too much fat and cholesterol in your blood could increase your risk for heart disease.
Swelling
Nephrotic syndrome can cause swelling of your legs, feet, and ankles, and sometimes of your hands and face. The medical term for swelling is edema.
Hypoalbuminemia
This is the term for low levels of albumin in your blood. Albumin is a protein that your liver makes. It stops fluid from leaking out of your bloodstream. Damage to the filters in your kidneys can allow albumin to leak out of your bloodstream.
Nephrotic Syndrome in Children
Nephrotic syndrome is rare in children. It affects fewer than 5 out of every 100,000 kids each year. Usually the cause is a kidney disease such as minimal change disease, but infections like hepatitis B, blood diseases like lymphoma, and certain medicines can also cause kidney damage. Some children have gene changes that cause them to be born with nephrotic syndrome.
Children with nephrotic syndrome have symptoms like these:
- Swelling around the eyes, especially in the morning
- Swelling in the face, hands, lower legs, feet, and belly
- Foamy pee
- Tiredness
Corticosteroids, also called steroids, are a common treatment for nephrotic syndrome in children. Often these anti-inflammatory medicines relieve symptoms enough to put the disease into remission.
Nephrotic Syndrome Risk Factors
Certain conditions such as diabetes, lupus, and amyloidosis make you more likely to get nephrotic syndrome.
You also face a greater risk if you take nonsteroidal anti-inflammatory drugs (NSAIDs) regularly.
Some infections can raise the chances you’ll get nephrotic syndrome. They include:
If you think you have symptoms of nephrotic syndrome, make an appointment with your doctor.
Nephrotic Syndrome Diagnosis
You’ll take a urine test, which will measure how much protein your kidneys are filtering out. You may also get blood tests that check on other kidney functions.
Your doctor might also check for diseases that could be a secondary cause of nephrotic syndrome, such as diabetes.
Some people will need a kidney biopsy, which requires taking a tissue sample for study under a microscope.
Nephrotic syndrome diagnosis criteria
Your doctor will look at these features of the disease to make the diagnosis:
Proteinuria. More than 3.5 grams of protein per deciliter (dL) of urine during a 24-hour period
Hypoalbuminemia. An albumin level of less than 3 grams per deciliter (dL) of blood
Peripheral edema. Swelling in your lower legs and hands
Nephrotic Syndrome Complications
Without treatment, nephrotic syndrome can cause other problems.
Nephrotic syndrome and cholesterol
Kidney damage leads to high levels of cholesterol and another type of fat called triglycerides in the blood. Having too much low-density lipoprotein (LDL) cholesterol and triglycerides increases your risk for a heart attack or of dying from a heart problem. High cholesterol also makes kidney disease worse.
Nephrotic syndrome and blood pressure
This disease can raise your blood pressure for a few reasons. When your kidneys are damaged, they can't remove enough sodium (salt) and fluid, both of which raise blood pressure. High blood pressure is also a side effect of some medicines that treat nephrotic syndrome, including corticosteroids and calcineurin inhibitors. Managing high blood pressure can help reduce your risk for heart disease.
Kidney failure
Nephrotic syndrome damages your kidneys. Over time, it can lead to kidney failure, which means your kidneys don't filter your blood well enough to meet your body's needs. If you develop kidney failure, you'll need dialysis or a kidney transplant.
Untreated nephrotic syndrome can also cause:
- Blood clots. These may form because you’ve lost too much protein from the blood, affecting your body’s ability to prevent clots.
- Infections such as pneumonia and meningitis because your body loses infection-fighting proteins called immunoglobulins.
Nephrotic Syndrome Treatment
Your doctor’s plan will depend on the cause of your nephrotic syndrome. If a different condition is to blame, that will be the first thing to treat. Lowering your cholesterol and blood pressure as well as reducing edema may be key goals.
Medicines you might take include:
- Blood-pressure medications called ACE inhibitors and ARBs, which curb the pressure in your glomeruli and lower the amount of protein in your urine
- Diuretics, or water pills, to reduce swelling
- Cholesterol-lowering drugs
- Blood thinners, or anticoagulants, to make blood clots less likely
- Medications that turn down your immune system, such as corticosteroids
You may need to cut down on salt to reduce swelling. Your doctor may also suggest you eat a diet low in saturated fats and cholesterol.
If your nephrotic syndrome doesn’t get better with these treatments, you might need dialysis, a treatment in which a machine filters your blood because your kidneys can’t do the job.
Diet for nephrotic syndrome
Your doctor may recommend that you go on a low-salt diet. Too much salt makes your body hold onto extra fluid, which raises blood pressure and causes swelling.
Avoid foods that are high in salt, like:
- Processed meats like salami and hot dogs
- Canned vegetables and soups
- Snack foods like pretzels and chips
- Sauces and salad dressings
You may also need to limit fluids, as drinking too much liquid also raises blood pressure.
Your doctor will do tests to check the levels of potassium and phosphate in your blood. High potassium levels are dangerous for your heart. If your levels are too high, you may need to cut down on foods that contain potassium and phosphate, such as:
- Fruits like bananas, melon, and nectarines
- Vegetables such as avocado, tomato, broccoli, and potatoes
- Milk and yogurt
- Nuts and seeds
- Chocolate
Nephrotic Syndrome vs. Nephritic Syndrome
Nephrotic syndrome is a kidney disorder caused by damage to the filtering glomeruli in your kidneys.
Nephritic syndrome is a group of symptoms like blood in your pee, high blood pressure, reduced urine, and swelling. These symptoms happen from inflammation in your glomeruli, called glomerulonephritis.
An infection like strep throat is the most common cause of nephritic syndrome in children. The infection triggers an immune system reaction that inflames the kidneys.
Causes of nephritic syndrome in adults include:
- Goodpasture syndrome, a disease in which the immune system attacks the kidney filters
- Lupus, an autoimmune disease
- IgA nephropathy, when a protein called immunoglobulin A builds up in the kidneys
- Hepatitis B or C
- Henoch-Schönlein purpura, a disease that causes purple spots on the skin and kidney problems
- Vasculitis, inflammation of the blood vessels
- Viral infections like measles, mumps, and mononucleosis
Nephrotic Syndrome Prevention
You can’t prevent some causes of nephrotic syndrome. But you can take action to avoid damage to your glomeruli:
- Manage high blood pressure and diabetes, if you have them.
- Be sure to get vaccines for common infections, especially if you work around people who have hepatitis or other diseases.
- If your doctor prescribes antibiotics, take them as directed and finish every prescription, even if you start to feel better.
Takeaways
Nephrotic syndrome is a group of symptoms that happen when the filters in your kidneys get damaged and too much protein leaks into your urine. It causes swelling in your feet and ankles, high blood pressure, and increased amounts of fat and cholesterol in your blood. Medicines can help lower your blood pressure and cholesterol. A low-salt, low-fluid diet is another important part of managing this condition.
Nephrotic Syndrome FAQs
What is the life expectancy of someone with nephrotic syndrome?
That depends on what caused nephrotic syndrome. Many people with minimal change disease go into long-term remission on corticosteroids and live a long, full life. Those with FSGS often progress to kidney failure and need dialysis or a kidney transplant. Your doctor can give you a better idea of your expected outcome.
Can nephrotic syndrome go away?
There's no cure for nephrotic syndrome, but some children grow out of the disease by their late teens or 20s. After 10 years, fewer than 1 in 5 kids still have nephrotic syndrome attacks.
Which autoimmune diseases cause nephrotic syndrome?
Lupus, type 1 diabetes, and membranous nephropathy can cause nephrotic syndrome. These autoimmune diseases attack and damage the kidneys.