From the Guidelines
Nephrotic syndrome is diagnosed when a patient presents with severe proteinuria (> 3.5 g/d) and serum albumin < 30 g/l, with or without edema, as defined by the most recent guideline 1. The diagnostic criteria for Nephrotic Syndrome (NS) include:
- Proteinuria: exceeding 3.5 grams per 24 hours in adults
- Hypoalbuminemia: serum albumin levels below 30 g/l
- Edema: typically peripheral and pitting, often appearing first around the eyes (periorbital) and in dependent areas like the ankles
- Hyperlipidemia: manifests as elevated cholesterol, triglycerides, and low-density lipoproteins These manifestations occur because damage to the glomerular filtration barrier allows proteins, particularly albumin, to leak into the urine, resulting in hypoalbuminemia, reduced plasma oncotic pressure, and fluid shifting from blood vessels into tissues, causing edema 1. Diagnosis requires a urinalysis showing proteinuria, blood tests confirming hypoalbuminemia and hyperlipidemia, and often a 24-hour urine collection to quantify protein excretion. A kidney biopsy may be necessary to determine the underlying cause, which could include minimal change disease, focal segmental glomerulosclerosis, membranous nephropathy, or other conditions, as noted in earlier studies 1. Key findings to evaluate for an underlying cause include the presence of nephrotic syndrome, absence of nephrotic syndrome, and exclusion of secondary forms of FSGS, as outlined in the most recent guideline 1.
From the Research
Diagnostic Criteria for Nephrotic Syndrome (NS)
The diagnostic criteria for Nephrotic Syndrome (NS) include:
- Proteinuria in excess of 3.5 g/24 hours 2, 3, 4, 5
- Hypoalbuminemia, typically less than 30 g/L 2
- Edema, which can be periorbital or dependent pitting oedema 2, 4
- Hyperlipidemia, including hypertriglyceridemia and hypercholesterolemia 2, 3, 6, 5
- Lipiduria 3
Clinical Presentation
Patients with NS typically present with:
- Periorbital oedema, most noticeable in the morning 2
- Dependent pitting oedema, more common later in the day 2
- Fatigue and swelling 6, 4
- Decreased urine output 4
Diagnostic Evaluation
The diagnosis of NS involves:
- Quantitative measurement of proteinuria, such as urine protein: creatinine ratio (PCR) or albumin: creatinine ratio (ACR) 2
- Renal biopsy to establish the underlying cause of glomerular disease 2, 5
- Additional tests to assess for secondary causes, such as systemic lupus erythematosus or amyloidosis 2