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.
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.
Tests and diagnosis
- 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.
Treatments and drugs
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.