ConditionKidneys & urinary tract
Nephrotic Syndrome
Nephrotic syndrome is a kidney disorder in which damaged filters (glomeruli) leak large amounts of protein into the urine. This causes low blood protein (albumin), swelling around the eyes, legs and belly, foamy urine and high cholesterol. In children it is usually minimal change disease, which responds well to steroids. In adults common causes include membranous nephropathy, FSGS, diabetes and amyloidosis. Treatment targets the cause, reduces swelling and protects against clots and infections.
Also called: Nephrosis, nephrotic range proteinuria, minimal change disease (most common childhood type)
At a glance
- What it is
- Heavy protein loss in the urine (over 3.5 g a day in adults) with low albumin and swelling.
- Children
- Usually minimal change disease, most often ages 2 to 8; responds to steroids.
- Adults
- Membranous nephropathy, FSGS, diabetic kidney disease, amyloidosis, lupus.
- Symptoms
- Puffy eyes, swollen legs and belly, foamy urine, weight gain, fatigue.
- Treatment
- Treat the cause (steroids, immunosuppressants), ACE inhibitors or ARBs, diuretics, low salt.
When to get help
Call 911 or go to the ER
- Shortness of breath, chest pain or coughing blood (possible clot in the lung): call 911 or your local emergency number
- A child with nephrotic syndrome who has fever with belly pain, vomiting or seems very unwell (possible peritonitis)
- Fainting, very little urine, or extreme swelling with difficulty breathing
See a doctor within a day or two
- A swollen, painful leg or sudden flank pain with blood in the urine (possible clot)
- Fever or signs of infection while on steroids or immunosuppressants
- A relapse in a child: protein on home dipstick tests for 3 days in a row
Book a routine appointment
- Puffy eyes in the morning, ankle swelling or foamy urine that persists
- Unexplained weight gain from fluid
What happens in nephrotic syndrome
Healthy kidney filters keep protein in the blood. In nephrotic syndrome, damage to the filter cells (podocytes) or the filter membrane makes it leaky. The result is a classic group of features:
- heavy proteinuria: more than 3.5 g of protein a day in adults (or a urine protein-to-creatinine ratio above about 3,000 mg/g)
- low blood albumin
- edema (fluid swelling)
- high cholesterol and triglycerides, as the liver makes more lipoproteins
Symptoms
- swelling around the eyes, especially in the morning
- swelling of the ankles, legs, genitals or belly (ascites)
- foamy or frothy urine
- weight gain from fluid
- tiredness and poor appetite
- in severe cases, breathlessness from fluid around the lungs
Nephrotic vs nephritic syndrome
| Nephrotic syndrome | Nephritic syndrome | |
|---|---|---|
| Main problem | Protein leak | Inflammation with blood leak |
| Urine | Very foamy, little blood | Cola-colored, blood and red cell casts |
| Protein | Heavy | Mild to moderate |
| Blood pressure | Often normal or mildly raised | Often high |
| Kidney function | Often normal early | Often reduced quickly |
Causes
In children
- minimal change disease: about 80 to 90 percent of cases in young children; filters look normal on a standard microscope
- FSGS and others, less commonly
- congenital nephrotic syndrome in the first months of life (rare, genetic)
In adults
| Cause | Notes |
|---|---|
| Membranous nephropathy | Common in adults; often autoimmune (anti-PLA2R antibodies); sometimes linked to cancer, hepatitis B or medicines |
| Focal segmental glomerulosclerosis (FSGS) | More common in Black adults (APOL1 variants); can be genetic or secondary to obesity or HIV |
| Minimal change disease | Can follow NSAID use or occur with lymphoma |
| Diabetic nephropathy | The most common secondary cause |
| Amyloidosis | Protein deposits in the kidney |
| Lupus nephritis | Membranous form |
| Infections | Hepatitis B and C, HIV, syphilis |
| Medicines | NSAIDs, gold, penicillamine, some cancer drugs |
Diagnosis
- urine dipstick and urine protein-to-creatinine ratio to measure protein loss
- blood tests: albumin, cholesterol, kidney function, blood sugar, complement levels, antibody tests (anti-PLA2R, ANA), hepatitis and HIV tests
- kidney biopsy: standard in adults to identify the cause; children with typical features usually start steroids without a biopsy
- ultrasound of the kidneys
Treatment
Treating the underlying disease
- children with minimal change disease: a course of oral corticosteroids; most go into remission within weeks
- adults: steroids for minimal change disease; immunosuppressants such as rituximab, calcineurin inhibitors or cyclophosphamide for membranous nephropathy or steroid-resistant disease, based on biopsy and risk
- treating diabetes, infections, lupus or amyloidosis
Supportive treatment
- ACE inhibitors or ARBs reduce protein leak and blood pressure
- SGLT2 inhibitors for some adults with chronic kidney disease
- diuretics for swelling, with careful monitoring
- low-salt diet, and fluid limits if swelling is severe
- statins for high cholesterol in persistent disease
- blood thinners in people at high clot risk, such as severe membranous nephropathy with very low albumin
Vaccinations
Pneumococcal and annual flu vaccines are recommended. Live vaccines are avoided during high-dose steroid or immunosuppressive treatment.
Complications
- blood clots, including deep vein thrombosis, pulmonary embolism and renal vein thrombosis, because clotting proteins rise and anticoagulant proteins are lost
- infections, including peritonitis and cellulitis, due to loss of antibodies
- acute kidney injury, especially with dehydration or excessive diuretics
- chronic kidney disease and kidney failure in some types
- high cholesterol and heart disease
- malnutrition and low vitamin D
Outlook
Most children with minimal change disease respond to steroids. Many relapse during childhood but grow out of it by adulthood, with normal kidney function. In adults, outcomes depend on the cause: minimal change disease responds well, membranous nephropathy often remits with treatment or spontaneously, while FSGS and diabetic disease more often progress to chronic kidney disease.
Frequently asked questions
What are the symptoms of nephrotic syndrome?
The main symptoms are swelling around the eyes, ankles, legs or belly, foamy urine, weight gain from fluid and tiredness. Blood tests show low albumin and high cholesterol, and urine tests show heavy protein loss.
What causes nephrotic syndrome?
In children, minimal change disease causes most cases. In adults, common causes include membranous nephropathy, FSGS, diabetic kidney disease, amyloidosis and lupus. Some infections and medicines such as NSAIDs can also trigger it.
Is nephrotic syndrome curable?
Often, yes. Most children with minimal change disease achieve remission with steroids and outgrow relapses. In adults, some types respond well to treatment, while others become chronic. Supportive treatment protects the kidneys in all cases.
Why does nephrotic syndrome cause foamy urine?
Protein in the urine lowers its surface tension, causing persistent foam or froth, like a beaten egg white. Occasional bubbles are normal; foam that persists every time is worth a urine test.
What is the difference between nephrotic and nephritic syndrome?
Nephrotic syndrome is mainly heavy protein leakage with swelling and little blood in the urine. Nephritic syndrome is inflammation causing blood in the urine, high blood pressure and reduced kidney function, with less protein loss.
Sources
This guide was written from current patient and clinical guidance, including:
- KDIGO: Clinical Practice Guideline for the Management of Glomerular Diseases
- NIDDK: Nephrotic Syndrome in Adults
- National Kidney Foundation: Nephrotic Syndrome
- American Academy of Pediatrics (HealthyChildren.org): Nephrotic Syndrome
- MedlinePlus: Nephrotic syndrome