What is nephrotic syndrome?

From the Guidelines

Nephrotic syndrome is a kidney disorder characterized by excessive protein loss in the urine, low blood protein levels, high cholesterol, and swelling, defined as presence of heavy proteinuria (≥ 1.0 g m−2 day−1 in children), hypoalbuminemia (< 3.0 g dl−1 in adults), and edema, as stated in the study by 1. The key features of nephrotic syndrome are:

• Proteinuria: Excessive protein in the urine (>3.5 g/day)
• Hypoalbuminemia: Low blood albumin levels (<3.0 g/dL)
• Edema: Swelling, typically in the legs, feet, and around the eyes
• Hyperlipidemia: High blood cholesterol and triglycerides This condition occurs when the kidneys' filtering units (glomeruli) are damaged, allowing large amounts of protein to leak into the urine, as noted in the study by 1. The loss of protein leads to fluid retention and other complications. Common causes include:

• Minimal change disease (most common in children)
• Focal segmental glomerulosclerosis
• Membranous nephropathy
• Diabetic nephropathy According to the study by 1, treatment typically involves:

1. Addressing the underlying cause
2. Reducing protein loss: ACE inhibitors or ARBs (e.g., enalapril 5-40 mg/day or losartan 25-100 mg/day)
3. Managing edema: Diuretics like furosemide (20-80 mg/day)
4. Controlling cholesterol: Statins (e.g., atorvastatin 10-80 mg/day)
5. Preventing complications: Anticoagulants if at risk for blood clots Patients should follow a low-sodium diet (less than 2 grams per day) and monitor their weight daily to track fluid retention, as recommended by 1. Regular follow-ups with a nephrologist are essential for monitoring kidney function and adjusting treatment as needed. Understanding nephrotic syndrome is crucial for proper management, as it can lead to serious complications like blood clots, infections, and progressive kidney damage if left untreated, as highlighted in the study by 1.

From the Research

Definition of Nephrotic Syndrome

Nephrotic syndrome is a clinical syndrome characterized by:

• Massive proteinuria (over 3.5 g per day in adults or 40 mg/m2 per hour in children) 2, 3, 4, 5, 6
• Hypoalbuminemia (less than 30 g/L) 3, 4, 5, 6
• Oncotic edema (peripheral edema) 2, 3, 4, 5, 6
• Hyperlipidemia 2, 3, 4, 5, 6

Pathophysiology

The main pathophysiological event in nephrotic syndrome is increased glomerular permeability due to:

• Immunological triggers 2, 3, 4, 5, 6
• Paraneoplastic triggers 2
• Genetic triggers 2, 4
• Infective triggers 2, 3, 5

Clinical Features

Patients with nephrotic syndrome typically present with:

• Periorbital edema (most noticeable in the morning) 3
• Dependent pitting edema (more common later in the day) 3
• Fatigue 4, 6
• Proteinuria, which should be documented by a quantitative measurement (e.g. urine protein: creatinine ratio or albumin: creatinine ratio) 3, 6

Complications

Nephrotic syndrome carries severe morbidity and mortality risk, with potential complications including:

• Venous thrombosis 3, 4, 6
• Hyperlipidemia 2, 3, 4, 5, 6
• Infection 3, 4, 6
• Acute kidney injury 3, 4, 6