What are the typical urine laboratory findings in a patient with nephrotic syndrome (nephrotic range proteinuria)?

From the Guidelines

Nephrotic syndrome is characterized by a urine protein-to-creatinine ratio greater than 3.5, or a spot urine total protein to creatinine ratio of 500 to 1,000 mg/g, as indicated by the most recent guidelines 1.

Key Laboratory Findings

• Significant proteinuria, typically exceeding 3.5 grams per 24 hours
• Urine protein-to-creatinine ratio greater than 3.5
• Spot urine total protein to creatinine ratio of 500 to 1,000 mg/g
• Urinalysis showing 3+ to 4+ protein on dipstick testing
• Microscopic examination of urine sediment revealing oval fat bodies and fatty casts

Diagnostic Criteria

• Urine albumin-to-creatinine ratio (uACR) ≥300 mg/g (≥30 mg/mmol) is considered severely increased albuminuria, which is typically seen in nephrotic syndrome 1
• Urine protein-to-creatinine ratio (uPCR) ≥500 mg/g (>50 mg/mmol) is also indicative of severely increased albuminuria

Clinical Implications

• Nephrotic syndrome is associated with hypoalbuminemia, edema, and hyperlipidemia
• The albumin-to-creatinine ratio is a continuous marker for cardiovascular event risk at all levels of kidney function
• Conventional qualitative tests for proteinuria may not detect small increases in urine albumin excretion, and tests to detect low concentrations of albumin are recommended 1

From the Research

Nephrotic Syndrome Urine Labs

• Nephrotic syndrome is characterized by hypoalbuminemia, severe proteinuria, and peripheral edema, frequently in conjunction with hyperlipidemia 2
• Proteinuria should be documented by a quantitative measurement e.g. urine protein: creatinine ratio (PCR) or albumin: creatinine ratio (ACR) 3
• PCR > 300-350 mg/mmol indicates nephrotic range proteinuria 3
• Urine labs for nephrotic syndrome typically include:
  • Urine protein: creatinine ratio (PCR)
  • Albumin: creatinine ratio (ACR)
  • Urine protein levels (> 3.5 g/24 hours) 3
• The diagnosis of nephrotic syndrome is based on a combination of clinical features, laboratory tests, and renal biopsy results 3, 2, 4

Key Laboratory Findings

• Hypoalbuminemia (< 30 g/L) 3
• Hyperlipidemia 3, 2, 4
• Proteinuria (> 3.5 g/24 hours) 3
• Hematuria (in some cases) 4
• Urine electrolytes and osmolality may also be abnormal in patients with nephrotic syndrome 5

Diagnostic Approach

• Patients with suspected nephrotic syndrome should undergo a thorough diagnostic evaluation, including urine labs, blood tests, and renal biopsy 3, 2, 4
• The diagnostic approach may vary depending on the patient's age, medical history, and underlying cause of nephrotic syndrome 4, 6