From the Guidelines
Nephrotic syndrome in adults is diagnosed when a patient presents with proteinuria > 3.5 g/d and serum albumin < 30 g/l, with or without edema, as defined by the KDIGO 2021 guideline for the management of glomerular diseases 1. The diagnostic criteria for Nephrotic Syndrome (NS) in adults prioritize the presence of significant proteinuria and hypoalbuminemia.
- Proteinuria is defined as > 3.5 g/d, which is a key indicator of glomerular damage and is typically assessed through a 24-hour urine collection or spot urine protein-to-creatinine ratio.
- Serum albumin levels should be < 30 g/l to meet the diagnostic criteria, reflecting the loss of albumin in the urine and subsequent hypoalbuminemia.
- Edema, although common, is not a required criterion for diagnosis but can be present, especially in dependent areas like the ankles, legs, and periorbital regions. The liver's response to protein loss, leading to hyperlipidemia, and the assessment of renal function through serum creatinine and blood urea nitrogen, are important considerations in the clinical evaluation of nephrotic syndrome. A kidney biopsy may be necessary to determine the underlying cause, especially in adults where primary glomerular diseases like membranous nephropathy, focal segmental glomerulosclerosis, and minimal change disease are common causes, as well as secondary causes such as diabetes, lupus, amyloidosis, and certain medications 1.
From the Research
Diagnostic Criteria for Nephrotic Syndrome (NS) in Adults
The diagnostic criteria for Nephrotic Syndrome (NS) in adults include:
- Nephrotic-range proteinuria (≥3.5g/24h) 2, 3
- Low serum albumin (< 30 g/L) 2, 3
- Edema, often associated with hyperlipidemia and lipiduria 2, 3, 4, 5
- Hyperlipidemia 2, 3, 4, 5
Clinical Features and Evaluation
Clinical features of NS in adults may include:
- Peripheral edema 3, 4, 5
- Fatigue 2, 4
- Proteinuria, which can be documented by a quantitative measurement such as urine protein: creatinine ratio (PCR) or albumin: creatinine ratio (ACR) 3
- Hypoalbuminemia, which can be confirmed by laboratory tests 2, 3, 4, 5 Evaluation of NS should assess for secondary causes, such as diabetes, amyloidosis, systemic lupus erythematosus, hematologic malignancies, and infections 3, 4, 5
Renal Biopsy and Diagnosis
Renal biopsy is often recommended to establish the underlying cause of NS, particularly in patients with suspected underlying systemic lupus erythematosus or other renal disorders 3, 4 A diagnosis of NS can be made despite the absence of nephrotic-range proteinuria, as seen in cases of systemic AL amyloidosis 2