Nephrotic Syndrome

What is nephrotic syndrome?

Nephrotic syndrome is not a single disease but a group of signs and symptoms that appear when the kidneys leak large amounts of protein into the urine. The kidneys contain millions of tiny filtering units called glomeruli (small clusters of blood vessels that clean the blood). In a healthy kidney, these filters keep important proteins in the bloodstream while removing waste and extra water. When the glomeruli are damaged, protein — especially a protein called albumin — escapes into the urine. The medical term for protein in the urine is proteinuria.

For many people searching for an answer to the question “what is nephrotic syndrome,” the simplest explanation is this: it is a kidney filtering problem that causes heavy protein loss in the urine, low protein levels in the blood, swelling in the body, and often raised cholesterol. Doctors usually confirm the diagnosis when all of these features are present together.

Nephrotic syndrome can affect people of any age. In children, it most often appears between the ages of about two and six, and in most childhood cases the underlying cause is a condition called minimal change disease. In adults, nephrotic syndrome is more often linked to other kidney diseases or to conditions that affect the whole body, such as diabetes or autoimmune disease (a condition in which the immune system attacks the body’s own tissues). The condition is usually managed by a nephrologist, a doctor who specializes in kidney disease. Within the Acibadem network, patients with this condition are typically cared for by the nephrology department, with pediatric nephrology teams involved for children.

Symptoms of nephrotic syndrome

Nephrotic syndrome symptoms often develop gradually, and swelling is usually the first change that people or parents notice. Because the blood loses protein, fluid shifts out of the blood vessels and collects in the body’s tissues. This fluid buildup is called edema.

Common nephrotic syndrome symptoms include:

• Swelling (edema): often first seen around the eyes, especially in the morning, and later in the ankles, feet, and legs. In more severe cases, fluid can collect in the abdomen or, less commonly, around the lungs.
• Foamy or frothy urine: caused by the large amount of protein passing into the urine.
• Weight gain: usually from retained fluid rather than fat.
• Tiredness and low energy: a common but nonspecific symptom.
• Loss of appetite: sometimes with a general feeling of being unwell.
• Reduced urine output in some cases, particularly when fluid retention is significant.

How symptoms appear can differ depending on the type and stage of the underlying kidney problem. In childhood minimal change disease, swelling often comes on relatively quickly and may follow a minor infection, and the condition typically responds well to treatment. In adults with slowly progressive kidney diseases, such as membranous nephropathy or diabetes-related kidney damage, swelling and other symptoms may develop more gradually over months. Some people have few obvious symptoms at first, and the protein loss is discovered on a routine urine test.

Nephrotic syndrome can also lead to complications, and sometimes these cause the first noticeable symptoms. People with the condition are more prone to infections, because protective antibody proteins are lost in the urine. They also have a higher risk of blood clots (the medical term is thrombosis), because clotting-control proteins are lost as well. A blood clot may cause sudden pain or swelling in one leg, or chest pain and breathlessness if it travels to the lungs. High cholesterol and raised blood pressure are common laboratory and clinical findings but usually do not cause symptoms on their own.

Causes and risk factors

Understanding nephrotic syndrome causes starts with the glomeruli. Anything that damages these filters — whether the damage begins in the kidney itself or comes from a disease affecting the whole body — can lead to protein leakage. Doctors group the causes into two broad categories.

Primary kidney causes

These conditions begin in the kidney itself:

• Minimal change disease: the most common cause in children. The glomeruli look almost normal under a standard microscope, which is how the disease gets its name. It usually responds well to steroid medication.
• Focal segmental glomerulosclerosis (FSGS): scarring in parts of some glomeruli. It is a common cause in adults and can be more difficult to treat.
• Membranous nephropathy: thickening of the glomerular filter membranes, often driven by the immune system. It is one of the most frequent causes in adults.

Secondary and systemic causes

These are diseases elsewhere in the body that damage the kidneys as one of their effects:

• Diabetes: long-standing diabetes is one of the most common causes of protein leakage and nephrotic syndrome in adults worldwide.
• Lupus (systemic lupus erythematosus): an autoimmune disease that can inflame the kidney filters, a condition called lupus nephritis.
• Amyloidosis: a condition in which abnormal proteins build up in organs, including the kidneys.
• Infections: certain infections, including hepatitis B, hepatitis C, and HIV, are linked to nephrotic syndrome in some patients.
• Medications: some drugs, including certain long-term pain relievers known as NSAIDs (nonsteroidal anti-inflammatory drugs), can occasionally trigger the condition.
• Certain cancers: in a small proportion of adults, nephrotic syndrome is associated with an underlying malignancy, which is one reason doctors evaluate adult patients thoroughly.

Risk factors include having diabetes, lupus, or another chronic condition that affects the kidneys; long-term use of medicines known to affect the kidneys; certain chronic infections; and, in some families, inherited (genetic) forms of kidney disease. In many childhood cases, however, no clear trigger is ever identified, and the condition is not caused by anything the child or family did.

Diagnosis of nephrotic syndrome

Nephrotic syndrome diagnosis is based on a combination of urine tests, blood tests, and, in many adults, a kidney biopsy. Doctors generally look for a specific set of findings that together define the syndrome: heavy protein in the urine, low albumin in the blood, swelling, and often high cholesterol.

Urine tests

A simple dipstick test can show whether protein is present in the urine. To measure how much, doctors use either a 24-hour urine collection (all urine passed in one day is collected and analyzed) or a spot urine protein-to-creatinine ratio, a single-sample test that estimates daily protein loss. In nephrotic syndrome, the protein loss is heavy — typically more than about 3 to 3.5 grams per day in adults, which is many times the normal amount.

Blood tests

Blood tests measure albumin (which is low in nephrotic syndrome because it is being lost in the urine), cholesterol and other blood fats (often raised), and creatinine (a waste product used to estimate how well the kidneys are filtering overall). Depending on the situation, doctors may also test for diabetes, lupus, hepatitis, HIV, and specific antibodies linked to membranous nephropathy, to look for an underlying cause.

Kidney biopsy

A kidney biopsy is a procedure in which a doctor removes a tiny sample of kidney tissue with a needle, usually under local anesthesia and ultrasound guidance, so it can be examined under a microscope. In adults, a biopsy is often needed to identify the exact type of kidney disease, because the result guides treatment. In young children with a typical presentation, doctors often start treatment for presumed minimal change disease without a biopsy, and reserve the biopsy for children who do not respond as expected or who have unusual features.

Imaging

An ultrasound scan of the kidneys is commonly performed to check kidney size and structure and to rule out other problems. Additional imaging may be ordered if a complication, such as a blood clot, is suspected.

Treatment options for nephrotic syndrome

Nephrotic syndrome treatment has two main goals: treating the underlying cause of the kidney damage, and controlling the symptoms and complications of protein loss. The right approach depends on the person’s age, the specific kidney disease found, and their overall health, so treatment plans vary considerably between patients.

Treating the underlying disease

• Corticosteroids: steroid medicines, such as prednisone, calm the immune system and are the standard first treatment for minimal change disease. Most children with this form respond well, although relapses (return of protein leakage) are common and may require repeated or longer courses.
• Other immune-suppressing medicines: when steroids do not work, cannot be tolerated, or relapses keep occurring, doctors may use other drugs that quiet the immune system. Examples include cyclophosphamide, calcineurin inhibitors (such as cyclosporine or tacrolimus), mycophenolate, and rituximab. The choice depends on the specific disease and the individual patient, and these medicines require careful monitoring for side effects.
• Treating the systemic cause: when nephrotic syndrome is secondary to another condition — for example diabetes, lupus, or an infection — managing that condition is central to protecting the kidneys.

Controlling symptoms and complications

• Diuretics: often called water pills, these medicines help the kidneys remove extra fluid and reduce swelling.
• Blood pressure medicines: drugs known as ACE inhibitors or ARBs lower blood pressure and also reduce the amount of protein leaking through the kidney filters, so they are frequently used even when blood pressure is only mildly raised.
• Cholesterol-lowering medicines: statins may be prescribed when blood fats remain high.
• Blood thinners (anticoagulants): in patients at higher risk of blood clots, doctors may recommend medication to reduce that risk, weighing the benefit against the risk of bleeding.
• Diet and fluid guidance: a low-salt diet helps limit fluid retention; in some cases doctors also advise moderating fluid intake. Protein intake is usually kept at a normal, balanced level rather than increased, and a dietitian’s input can be helpful.
• Vaccinations and infection care: because infection risk is higher, doctors often recommend appropriate vaccinations and prompt treatment of infections; live vaccines may need to be delayed during immune-suppressing treatment.

Watchful waiting, procedures, and advanced options

In some situations — for example, certain adults with membranous nephropathy and relatively mild disease — doctors may recommend a period of supportive care and monitoring before starting immune-suppressing drugs, because a proportion of these cases improve on their own. Surgery is not a treatment for nephrotic syndrome itself. However, if the underlying disease progresses over years to advanced kidney failure despite treatment, options such as dialysis (a treatment that filters the blood when the kidneys cannot) or kidney transplantation may eventually be discussed. This outcome is not typical for the forms that respond well to medication, such as most childhood minimal change disease.

Living with nephrotic syndrome and outlook

The outlook for nephrotic syndrome varies widely and depends mainly on the underlying cause, how well it responds to treatment, and how well complications are controlled. Most children with minimal change disease respond to steroids and, although relapses are common during childhood, many eventually outgrow the condition and keep normal kidney function in the long term. In adults, the course depends on the specific kidney disease: some cases go into remission (a period when protein leakage stops) with or without treatment, some follow a relapsing pattern, and some progress slowly despite therapy. No doctor can promise a particular outcome, and honest, ongoing conversations with the care team are important.

Day to day, living with nephrotic syndrome usually involves regular follow-up visits, urine and blood tests to monitor protein levels and kidney function, and attention to medication schedules. Many patients or parents learn to check urine for protein at home with dipsticks, which can help detect a relapse early. Practical steps that many care teams recommend include following a low-salt diet, keeping blood pressure and blood sugar well controlled, staying up to date with recommended vaccinations, avoiding smoking, maintaining a healthy weight, and checking with a doctor or pharmacist before taking new medicines — including over-the-counter pain relievers — because some can strain the kidneys. Living with a chronic condition can also be emotionally demanding, particularly for families of young children, and support from the care team, counselors, or patient groups can be valuable.

Frequently asked questions

What is nephrotic syndrome in simple terms?

Nephrotic syndrome means the kidney’s filters are leaking large amounts of protein into the urine. This lowers protein levels in the blood, which causes fluid to build up in the body and leads to swelling, often around the eyes, ankles, and legs. It is a pattern of findings rather than one single disease, and several different kidney conditions can cause it.

Can nephrotic syndrome heal or go away?

In many cases, yes — particularly in children with minimal change disease, which usually responds to steroid treatment, although relapses can occur before the condition eventually settles. In adults, the answer depends on the underlying cause: some forms go into remission with treatment or even on their own, while others need long-term management. Your doctor can explain what is most likely in your specific situation, but no outcome can be guaranteed.

How serious is nephrotic syndrome?

Seriousness varies. When it responds well to treatment, many people do well and keep normal kidney function. Without treatment, or in forms that do not respond, complications such as infections, blood clots, very high cholesterol, and gradual loss of kidney function can occur. This is why medical follow-up and adherence to treatment are important even when symptoms improve.

What causes nephrotic syndrome in children compared with adults?

In children, the most common cause is minimal change disease, and often no trigger is ever identified. In adults, nephrotic syndrome causes more often include diseases such as focal segmental glomerulosclerosis, membranous nephropathy, diabetes, and lupus. Because the causes differ, the diagnostic approach also differs: adults usually need a kidney biopsy, while many children are treated first and biopsied only if treatment does not work as expected.

What does nephrotic syndrome treatment usually involve?

Treatment typically combines medicines that target the underlying disease — often steroids or other immune-suppressing drugs — with supportive measures such as diuretics for swelling, blood pressure medicines that also reduce protein leakage, cholesterol-lowering drugs when needed, and a low-salt diet. The exact plan depends on the cause found on testing, so two patients with nephrotic syndrome may receive quite different treatments.

How is nephrotic syndrome diagnosed?

Doctors confirm the diagnosis with urine tests showing heavy protein loss, blood tests showing low albumin and often high cholesterol, and a clinical assessment of swelling. A kidney ultrasound is commonly done, and many adults have a kidney biopsy to identify the exact disease affecting the filters, because this guides treatment choices.

Does nephrotic syndrome come back after treatment?

It can. Relapses are common in childhood minimal change disease, often triggered by minor infections, and some adult forms also follow a relapsing course. Doctors usually teach patients or parents how to watch for early signs, such as returning swelling or protein on a home urine dipstick, so that treatment can be restarted promptly if needed.

When to see a doctor

Anyone who notices new or worsening swelling — especially around the eyes in the morning or in the legs and ankles — together with foamy urine or unexplained weight gain should see a doctor for evaluation. If you have already been diagnosed with nephrotic syndrome, contact your care team if swelling returns, urine becomes foamy again, or a home dipstick shows protein, as these may signal a relapse.

Seek urgent medical care if you or your child experiences any of the following red-flag warning signs:

• Sudden chest pain or breathlessness — possible signs of a blood clot in the lungs.
• Sudden pain, warmth, or swelling in one leg — possible signs of a blood clot in a leg vein.
• Fever, severe abdominal pain, or signs of infection — infections can become serious more quickly in people with nephrotic syndrome, particularly during immune-suppressing treatment.
• Rapidly increasing swelling of the abdomen, face, or whole body, or difficulty breathing when lying flat.
• Passing very little urine or none at all.
• Severe headache, confusion, or vision changes, which can accompany dangerously high blood pressure.

Prompt assessment matters, because complications such as blood clots and serious infections are treatable when caught early. If you are unsure whether a symptom is urgent, it is safer to be checked by a medical professional.