From the Guidelines
Nephrotic syndrome is defined as the presence of heavy proteinuria (≥ 3.5 g day−1), hypoalbuminemia (< 3.0 g dl−1 in adults), and edema, with hypercholesterolemia commonly present. According to the study published in Kidney International in 2007 1, the definition of nephrotic syndrome includes these key characteristics. The study notes that nephrotic syndrome can be associated with various etiological agents, but the focus is on primary glomerular disease of idiopathic cause, with minimal change disease, focal segmental glomerulosclerosis, and membranous nephropathy being the leading histologic variants. Some key features of nephrotic syndrome include:
- Heavy proteinuria, defined as ≥ 1.0 g m−2 day−1 in children or ≥ 3.5 g day−1 in adults
- Hypoalbuminemia, with levels < 3.0 g dl−1 in adults or < 2.5 g dl−1 in children
- Edema, which is commonly present
- Hypercholesterolemia, which is also commonly present The underlying causes of nephrotic syndrome can be primary or secondary, with primary causes including diseases that affect only the kidneys, such as minimal change disease, focal segmental glomerulosclerosis, and membranous nephropathy, as noted in the study 1.
From the Research
Definition of Nephrotic Syndrome
Nephrotic syndrome is characterized by:
- Hypoalbuminemia (< 30 g/L) 2
- Severe proteinuria (> 3.5 g/24 hours) 2
- Peripheral edema 2, 3, 4, 5
- Often associated with hyperlipidemia 6, 2, 3, 5
Key Features
- Loss of plasma proteins in the urine is the primary process leading to the nephrotic syndrome 6
- Increased permeability to proteins at the level of the glomerulus, allowing for passage of albumin and other proteins into the urine 4
- Proteinuria leads to a cascade of clinical complications characterized by fluid accumulation, kidney inflammation, and dysregulation of coagulation and immunity 4
Diagnosis
- Diagnosis is based on typical clinical features with confirmation of heavy proteinuria and hypoalbuminemia 2, 5
- Quantitative measurement of proteinuria, such as urine protein: creatinine ratio (PCR) or albumin: creatinine ratio (ACR) 2
- Renal biopsy is often recommended to establish the underlying cause of nephrotic syndrome 6, 2, 5