Nephrotic syndrome

Nephrotic syndrome is one of the most common causes of low albumin, heavy proteinuria, and unexplained swelling—and is often first detected through routine lab testing.

It is a kidney disease characterized by excessive protein loss in the urine (typically more than 3.5 grams per day). This occurs when the kidneys’ filtering units become damaged and less effective, allowing large amounts of protein to pass into the urine.

Because this protein loss disrupts normal fluid balance, it leads to a recognizable set of findings: low blood albumin (hypoalbuminemia), fluid retention (edema), high cholesterol and triglycerides (hyperlipidemia), and fat in the urine (lipiduria).

Common Causes

Nephrotic syndrome can result from diseases that directly affect the kidneys or from systemic conditions:

Primary kidney diseases include:
- Focal segmental glomerulosclerosis (FSGS)
- Membranous nephropathy
- Minimal change disease
Secondary causes include:
- Diabetic nephropathy
- Lupus nephritis
- Certain infections, medications, or cancers

In children, minimal change disease is the most common cause and often responds well to treatment.

Key Biomarkers & Tests

Diagnosis and monitoring rely on a combination of urine and blood tests:

Urine albumin-to-creatinine ratio (ACR)
Total urine protein
Serum albumin
Total protein
Lipid panel (cholesterol and triglycerides)
Creatinine
Estimated glomerular filtration rate (eGFR)

A kidney biopsy may be needed to confirm the underlying cause and guide treatment decisions.

Symptoms

Swelling (edema) due to fluid retention
Foamy or frothy urine (a sign of protein loss)
Rapid weight gain from fluid buildup
Fatigue
Decreased urine output in some cases

Complications

If not properly managed, nephrotic syndrome can lead to:

Increased risk of infections (due to loss of immune proteins)
Blood clots (due to loss of natural anticoagulants)
Acute kidney injury
Chronic kidney disease (CKD)
Cardiovascular disease from prolonged high cholesterol

Many of these complications can be detected early through regular blood tests—falling albumin, rising creatinine, or worsening lipid levels are often the first signs that the condition is progressing.

Treatment & Management

Treatment depends on the underlying cause but focuses on reducing protein loss, managing symptoms, and preventing complications:

Corticosteroids or immunosuppressive medications (especially for primary kidney diseases)
ACE inhibitors or ARBs to reduce proteinuria
Diuretics to manage fluid retention
Statins to control cholesterol levels
Dietary changes, such as reducing sodium intake

Many patients achieve remission with appropriate treatment, although some develop chronic kidney disease, making long-term lab monitoring essential for catching progression early.