By Mayo Clinic Staff
Nephrotic syndrome is a kidney disorder that causes your body to excrete too much protein in your urine.
Nephrotic syndrome is usually caused by damage to the clusters of small blood vessels in your kidneys that filter waste and excess water from your blood. Nephrotic syndrome causes swelling (edema), particularly in your feet and ankles, and increases the risk of other health problems.
Treatment for nephrotic syndrome includes treating the underlying condition that's causing it and taking medications. Nephrotic syndrome can increase your risk of infections and blood clots. Your doctor may recommend medications and dietary changes to prevent these and other complications of nephrotic syndrome.
Signs and symptoms of nephrotic syndrome include:
- Severe swelling (edema), particularly around your eyes and in your ankles and feet
- Foamy urine, which may be caused by excess protein in your urine
- Weight gain due to excess fluid retention
When to see a doctor
Make an appointment with your doctor if you have any signs or symptoms that worry you.
Nephrotic syndrome is usually caused by damage to the clusters of tiny blood vessels (glomeruli) of your kidneys.
The glomeruli filter your blood as it passes through your kidneys, separating things your body needs from those it doesn't. Healthy glomeruli keep blood protein (mainly albumin) — which is needed to maintain the right amount of fluid in your body — from seeping into your urine. When damaged, glomeruli allow too much blood protein to leave your body, leading to nephrotic syndrome.
Many possible causes
Many diseases and conditions can cause glomerular damage and lead to nephrotic syndrome, including:
- Minimal change disease. The most common cause of nephrotic syndrome in children, this disorder results in abnormal kidney function, but when the kidney tissue is examined under a microscope, it appears normal or nearly normal. The cause of the abnormal function typically can't be determined.
- Focal segmental glomerulosclerosis. Characterized by scattered scarring of some of the glomeruli, this condition may result from another disease or a genetic defect or occur for no known reason.
- Membranous nephropathy. This kidney disorder is the result of thickening membranes within the glomeruli. The exact cause of the thickening isn't known, but it's sometimes associated with other medical conditions, such as hepatitis B, malaria, lupus and cancer.
- Diabetic kidney disease. Diabetes can lead to kidney damage (diabetic nephropathy) that affects the glomeruli.
- Systemic lupus erythematosus. This chronic inflammatory disease can lead to serious kidney damage.
- Amyloidosis. This disorder occurs when substances called amyloid proteins accumulate in your organs. Amyloid buildup often affects the kidneys, damaging their filtering system.
- Blood clot in a kidney vein. Renal vein thrombosis, which occurs when a blood clot blocks a vein connected to the kidney, can cause nephrotic syndrome.
- Heart failure. Some forms of heart failure, such as constrictive pericarditis and severe right heart failure, can cause nephrotic syndrome.
Factors that can increase your risk of nephrotic syndrome include:
- Medical conditions that can damage your kidneys. Certain diseases and conditions increase your risk of developing nephrotic syndrome, such as diabetes, lupus, amyloidosis, minimal change disease and other kidney diseases.
- Certain medications. Examples of medications that can cause nephrotic syndrome include nonsteroidal anti-inflammatory drugs and drugs used to fight infections.
- Certain infections. Examples of infections that increase the risk of nephrotic syndrome include HIV, hepatitis B, hepatitis C and malaria.
Possible complications of nephrotic syndrome include:
- Blood clots. The inability of the glomeruli to filter blood properly can lead to loss of blood proteins that help prevent clotting. This increases your risk of developing a blood clot (thrombus) in your veins.
- High blood cholesterol and elevated blood triglycerides. When the level of the protein albumin in your blood falls, your liver makes more albumin. At the same time, your liver releases more cholesterol and triglycerides.
- Poor nutrition. Loss of too much blood protein can result in malnutrition. This can lead to weight loss, but it may be masked by swelling. You may also have too few red blood cells (anemia) and low levels of vitamin D and calcium.
- High blood pressure. Damage to your glomeruli and the resulting buildup of wastes in your bloodstream (uremia) can raise your blood pressure.
- Acute kidney failure. If your kidneys lose their ability to filter blood due to damage to the glomeruli, waste products may build up quickly in your blood. If this happens, you may need emergency dialysis — an artificial means of removing extra fluids and waste from your blood — typically with an artificial kidney machine (dialyzer).
- Chronic kidney disease. Nephrotic syndrome may cause your kidneys to gradually lose their function over time. If kidney function falls low enough, you may require dialysis or a kidney transplant.
- Infections. People with nephrotic syndrome have an increased risk of infections.
If you have signs and symptoms that cause concern, start by seeing your family doctor or a general practitioner. If your doctor suspects you may have a kidney problem, such as nephrotic syndrome, you may be referred to a doctor who specializes in the kidneys (nephrologist).
Here's some information to help you get ready for your appointment and what to expect from your doctor.
What you can do
Before your appointment:
- Be aware of any pre-appointment restrictions. When you make the appointment, ask if there's anything you need to do in advance, such as restrict your diet.
- Write down symptoms you're experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment.
- Write down key personal information, including any major stresses or recent life changes.
- Make a list of all medications, vitamins or supplements that you're taking.
- Consider taking a family member or friend along, to help you remember all the information provided during the appointment.
- Write down questions to ask your doctor.
Preparing a list of questions ahead of time can help you make the most of your time with your doctor. For nephrotic syndrome, some basic questions to ask your doctor include:
- What's the most likely cause of my nephrotic syndrome?
- What tests do I need?
- Is this condition likely temporary, or will I always have it?
- What are my treatment options? And which do you recommend for me?
- What are the risks and benefits of each treatment?
- Are there changes I can make to my diet to help me feel better? Could a dietitian help me?
- I have other health conditions. How can I best manage these conditions together?
- Is there a generic alternative to the medicine you're prescribing me?
- Are there brochures or other printed material that I can take with me? What websites do you recommend?
- How do I know when I need to plan for a follow-up visit? Are there any symptoms that suggest I should call for advice right away?
In addition to the questions that you prepare ahead of time, don't hesitate to ask other questions that occur to you during your visit.
What to expect from your doctor
Your doctor is likely to ask you a number of questions, such as:
- When did you first notice your symptoms?
- Do your symptoms come and go, or do you have them all the time?
- How severe are your symptoms?
- Does anything seem to improve your symptoms?
- What, if anything, appears to worsen your symptoms?
Tests and procedures used to diagnose nephrotic syndrome include:
- Urine tests. A urinalysis can reveal abnormalities in your urine, such as large amounts of protein, if you have nephrotic syndrome. You may be asked to collect urine samples over 24 hours for an accurate measure of the protein in your urine.
- Blood tests. If you have nephrotic syndrome, a blood test may show low levels of the protein albumin (hypoalbuminemia) specifically and often decreased levels of blood protein overall. Loss of albumin is often associated with an increase in blood cholesterol and blood triglycerides. Serum creatinine and blood urea also may be measured to assess your overall kidney function.
- Removing a sample of kidney tissue for testing. Your doctor may recommend a procedure called a kidney biopsy to remove a small sample of kidney tissue for testing. During a kidney biopsy, a special needle is inserted through your skin and into your kidney. Kidney tissue is collected and sent to a lab for testing.
Treatment for nephrotic syndrome involves treating any underlying medical condition that may be causing your nephrotic syndrome. Your doctor may also recommend medications that may help control your signs and symptoms or treat complications of nephrotic syndrome. Medications may include:
- Blood pressure medications. Drugs called angiotensin-converting enzyme inhibitors reduce blood pressure and also reduce the amount of protein released in urine. Medications in this category include benazepril (Lotensin), captopril (Capoten) and enalapril (Vasotec). Another group of drugs that works in a similar way is called angiotensin II receptor blockers and includes losartan (Cozaar) and valsartan (Diovan).
- Water pills. Water pills (diuretics) help control swelling by increasing your kidneys' fluid output. Diuretic medications include furosemide (Lasix) and spironolactone (Aldactone).
- Cholesterol-reducing medications. Medications called statins can help lower cholesterol levels. However, it's currently unclear whether or not cholesterol-lowering medications can specifically improve the outcomes of people with nephrotic syndrome, such as avoiding heart attacks or decreasing the risk of early death. Statins include atorvastatin (Lipitor), fluvastatin (Lescol), lovastatin (Altoprev, Mevacor), pravastatin (Pravachol), rosuvastatin (Crestor) and simvastatin (Zocor).
- Blood thinners. Medications called anticoagulants help decrease your blood's ability to clot and reduce your risk of developing blood clots. Anticoagulants include heparin or warfarin (Coumadin).
- Immune system-suppressing medications. Medications to control the immune system, such as corticosteroids, may decrease the inflammation that accompanies certain kidney disorders, such as minimal change disease.
Changes to your diet may help you cope with nephrotic syndrome. Your doctor may refer you to a dietitian to discuss how what you eat can help you cope with the complications of nephrotic syndrome. A dietitian may recommend that you:
- Choose lean sources of protein
- Reduce the amount of fat and cholesterol in your diet to help control your blood cholesterol levels
- Eat a low-salt diet to help control the swelling (edema) you experience
Dec. 18, 2014
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