Nephrotic syndrome is a group of symptoms that indicate that the kidneys are not functioning as they should. Nephrotic syndrome can result from diseases that affect just the kidneys or the entire body. It can occur in both adults and children.
According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), diabetes is the systemic disease that most commonly causes nephrotic syndrome, while focal segmental glomerulosclerosis (FSGS) is the kidney-related condition most likely to cause it.
In this article, we look at what nephrotic syndrome is, its causes, and how to manage and treat the condition.
The NIDDK state that nephrotic syndrome occurs when tiny blood vessels in the kidneys, called glomeruli, are not working properly.
The glomeruli normally act as filters, removing water and waste molecules from the blood and sending them to the bladder in the form of urine. These vessels also allow blood cells and large molecules, such as proteins, to stay in the blood.
When the glomeruli become damaged, protein may be able to seep through the filter system into the urine.
Nephrotic syndrome involves the following signs:
- Albuminuria: High levels of protein are present in the urine.
- Hypoalbumenia: There are low levels of a protein called albumin in the blood.
- Hyperlipidemia: There are elevated levels of fat and cholesterol in the blood.
Damage to the glomeruli also may cause a condition called nephritic syndrome. As with nephrotic syndrome, the symptoms of nephritic syndrome include protein in the urine.
However, the protein levels are usually not as high as they are in nephrotic syndrome. A person with nephritic syndrome may also notice blood in the urine, which is not a symptom of nephrotic syndrome.
The symptoms of nephrotic syndrome include:
- swelling or edema, typically in the ankles, feet, or legs
- loss of appetite
- weight gain
- foamy urine
The foaming that occurs due to the presence of protein in the urine is different than the bubbles that a person may notice in normal urine.
A 2019 article in the Clinical Journal of the American Society of Nephrology states that the foam appears as layers of small-to-medium bubbles that do not disperse easily. In contrast, normal urine may contain a single layer of larger bubbles that soon disappear.
People with nephrotic syndrome might first notice swelling or edema in their legs after standing for a long time or puffiness around their eyes after waking up.
As the condition progresses, the person might find that their legs are always swollen or notice swelling in other parts of the body.
Healthcare professionals classify the cause of nephrotic syndrome as either primary or secondary.
The NIDDK define these terms as follows:
Primary causes of nephrotic syndrome are conditions that only affect the kidneys.
Examples of primary causes include:
- FSGS: In FSGS, scarring occurs in portions of the glomeruli. FSGS occurs more frequently in males than females and has a higher prevalence among African American people.
- Membranous nephropathy: Immune complexes build up in the glomeruli, causing damage.
- Minimal change disease (MCD): The damage to the glomeruli is only visible with a very powerful microscope. MCD is the most common cause of nephrotic syndrome in children. In adults, allergies, infections, or certain medications may cause MCD.
- Membranoproliferative glomerulonephritis (MPGN): The immune system attacks cells in the kidneys, damaging the glomeruli. Sometimes, another disease, such as hepatitis C, causes MPGN.
Secondary causes are conditions that affect the entire body, resulting in nephrotic syndrome.
Some examples of secondary causes are:
The NIDDK state that nephrotic syndrome may resolve once a person has treated the underlying cause.
For example, MCD rarely results in kidney failure, and most people recover and avoid relapses.
However, some other conditions that cause nephrotic syndrome are chronic and may progress over time, such as diabetes.
A person should see a healthcare professional to create a treatment plan.
The treatment of nephrotic syndrome varies depending on its cause. However, it typically includes medications to treat the underlying cause, as well as changes in diet.
Some possible drug treatments include:
- Steroids: Doctors may prescribe steroids to treat MCD in children or adults.
- Diuretics: These may help the body remove excess fluid and reduce swelling.
- Angiotensin converting enzyme (ACE) inhibitors or angiotensin receptor blockers: These can help control blood pressure and may reduce protein in the urine.
- Immunosuppressive drugs: These may help in conditions such as FSGS, in which a person’s immune system is attacking the glomeruli.
- Statins: These can lower cholesterol.
A person should also get the pneumococcal vaccine.
Dietary changes that might help in treating nephrotic syndrome include:
Complications of nephrotic syndrome often result from the loss of certain proteins in the urine.
The body may need these proteins to fight infections or control blood clotting.
Other nephrotic syndrome complications may include:
- coronary artery disease
- high blood pressure
- anemia, which is when a person does not have enough healthy red blood cells
- hypothyroidism, which occurs when the thyroid gland is unable to produce enough thyroid hormone
- temporary loss of kidney function
In addition to a physical exam and medical history, a doctor will typically diagnose nephrotic syndrome using the following tests:
- Urine test: This test looks for elevated levels of protein in the urine.
- Blood test: This test may reveal the levels of albumin, cholesterol, and other blood components.
- Kidney biopsy: A doctor might request a biopsy to look for microscopic changes in the kidney.
- Ultrasound: Doctors sometimes use this type of imaging to see whether the kidneys look normal.
Someone who is experiencing symptoms of nephrotic syndrome, such as foamy urine, loss of appetite, and edema, should contact a doctor.
They should also contact a doctor if their symptoms get worse or new symptoms appear.
Nephrotic syndrome is a group of symptoms that can indicate kidney damage. The signs and symptoms typically include swelling, fatigue, foamy urine, large amounts of protein in the urine, and low albumin levels and high cholesterol levels in the blood.
Pinpointing the cause of the condition will help doctors determine the best course of treatment.