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
Loss of appetite
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:
Diabetic kidney disease. Diabetes can lead to kidney damage (diabetic nephropathy) that affects the glomeruli.
Minimal change disease. This is the most common cause of nephrotic syndrome in children. Minimal change disease 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.
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.
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 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.
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 (ACE) inhibitors reduce blood pressure and also reduce the amount of protein released in urine. Medications in this category include benazepril (Lotensin), captopril and enalapril (Vasotec). Another group of drugs that works in a similar way is called angiotensin II receptor blockers (ARBs) and includes losartan (Cozaar) and valsartan (Diovan). Other medications, such as renin inhibitors, also may be used, though ACE inhibitors and ARBs are generally used first.
Water pills. Water pills (diuretics) help control swelling by increasing your kidneys' fluid output. Diuretic medications typically include furosemide (Lasix). Others may include spironolactone (Aldactone) and thiazides, such as hydrochlorothiazide.
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 attack
s or decreasing the risk of early death. Statins include atorvastatin (Lipitor), fluvastatin (Lescol), lovastatin (Altoprev), pravastatin (Pravachol), rosuvastatin (Crestor) and simvastatin (Zocor).
Blood thinners. Medications called anticoagulants help decrease your blood's ability to clot and may be prescribed if you've had a blood clot to reduce your risk of future blood clots. Anticoagulants include heparin, warfarin (Coumadin, Jantoven), dabigatran (Pradaxa), apixaban (Eliquis) and rivaroxaban (Xarelto).
Immune system-suppressing medications. Medications to control the immune system, such as corticosteroids, may decrease the inflammation that accompanies underlying conditions, such as minimal change disease, lupus and amyloidosis.