Nephrotic syndrome

Definition

Nephrotic syndrome is a group of symptoms including protein in the urine (more than 3.5 grams per day), low blood protein levels, high cholesterol levels, high triglyceride levels, and swelling.

Alternative Names

Nephrosis

Causes, incidence, and risk factors

Nephrotic syndrome is caused by various disorders that damage the kidneys, particularly the basement membrane of the glomerulus. This immediately causes abnormal excretion of protein in the urine.

The most common cause in children is minimal change disease, while membranous glomerulonephritis is the most common cause in adults.

This condition can also occur as a result of infection (such as strep throat, hepatitis, or mononucleosis), use of certain drugs, cancer, genetic disorders, immune disorders, or diseases that affect multiple body systems including diabetes, systemic lupus erythematosus, multiple myeloma, and amyloidosis.

It can accompany kidney disorders such as glomerulonephritis, focal and segmental glomerulosclerosis, and mesangiocapillary glomerulonephritis.

Nephrotic syndrome can affect all age groups. In children, it is most common from age 2 to 6. This disorder occurs slightly more often in males than females.

Symptoms

Swelling (edema) is the most common symptom. It may occur:

• In the face and around the eyes (facial swelling)
• In the arms and legs, especially in the feet and ankles
• In the belly area (swollen abdomen)

Other symptoms include:

• Foamy appearance of the urine
• Weight gain (unintentional) from fluid retention
• Poor appetite
• High blood pressure

Signs and tests

The doctor will perform a physical exam. Laboratory tests will be done to see how well the kidneys are working. They include:

• Creatine - blood test
• Blood urea nitrogen (BUN)
• Creatinine clearance
• Albumin blood test - may be low
• Urinalysis - reveals large amounts of urine protein

Fats are often also present in the urine. Blood cholesterol and triglyceride levels may increase.

Kidney biopsy may be needed .

Tests to rule out various causes may include the following:

• Glucose tolerance test
• Antinuclear antibody
• Rheumatoid factor
• Cryoglobulins
• Complement levels
• Hepatitis B and C antibodies
• VDRL serology
• Serum protein electrophoresis

• Urinary casts
• Protein electrophoresis - urine
• Serum iron

Treatment

The goals of treatment are to relieve symptoms, prevent complications and delay progressive kidney damage. Treatment of the disorder that causes the condition is necessary to control nephrotic syndrome. Treatment may be needed for life.

Controlling blood pressure is the most important measure to delay kidney damage. The goal is to keep blood pressure at or below 130/80 mmHg. Angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs) are the medicines most often used in this case. ACE inhibitors may also help decrease the amount of protein loss in the urine.

Corticosteroids and other drugs that suppress or quiet the immune system may be used.

High cholesterol and levels should be treated to reduce the risk of heart and blood vessel problems. However, a low-fat, low-cholesterol diet is usually not as helpful for people with nephrotic syndrome. Medications to reduce cholesterol and triglycerides may be needed, most commonly statins.

A low salt diet may help with swelling in the hands and legs. Water pills (diuretics) may also help with this problem.

Low protein diets may or may not be helpful. A moderate-protein diet (1 gram of protein per kilogram of body weight per day) may be suggested.

Vitamin D may need to be replaced if nephrotic syndrome is chronic and unresponsive to therapy.

Blood thinners may be required to treat or prevent clot formation.

Expectations (prognosis)

The outcome varies; the syndrome may be acute and short-term or chronic and unresponsive to therapy. The cause and development of complications also affects the outcome.

Complications

• Atherosclerosis and related heart diseases
• Renal vein thrombosis
• Acute kidney failure
• Chronic kidney disease
• Infections, including pneumococcal pneumonia
• Malnutrition
• Fluid overload, congestive heart failure, pulmonary edema

Calling your health care provider

Call your health care provider if symptoms which may indicate nephrotic syndrome occur.

Call your health care provider if nephrotic syndrome persists or if new symptoms develop, including severe headache, fever, sores on the skin, cough, discomfort with urination, or decreased urine output.

Go to the emergency room or call the local emergency number (such as 911) if convulsions occur.

Prevention

Appropriate treatment of conditions that can cause nephrotic syndrome may help prevent the syndrome.

References

In: Brenner BM, ed. Brenner: Brenner and Rector's the Kidney. 8th ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 30.