What are the complications of nephrotic syndrome?

Complications of Nephrotic Syndrome

Nephrotic syndrome leads to multiple life-threatening complications including thromboembolism, severe infections, progressive kidney failure, cardiovascular disease, and acute kidney injury—all driven by massive proteinuria and hypoalbuminemia.

Major Complications by System

Thromboembolic Complications

• The hypercoagulable state becomes clinically significant when serum albumin falls below 2.9 g/dL, though this threshold varies by assay method 1.
• Urinary loss of natural anticoagulants (antithrombin III, protein C, protein S) combined with hepatic overproduction of procoagulant factors creates a prothrombotic environment 2.
• Venous thromboembolism (including renal vein thrombosis) and arterial events are well-documented complications requiring vigilant monitoring 3.
• KDIGO 2021 emphasizes monitoring drug interactions between anticoagulants (particularly warfarin) and antibiotics like azithromycin in patients requiring thromboprophylaxis 4.

Infectious Complications

• Patients with nephrotic syndrome have markedly increased risk of bacterial infections, particularly cellulitis and spontaneous bacterial peritonitis 4.
• The infection risk stems from multiple mechanisms: urinary loss of immunoglobulins, loss of complement factors, edema-related skin breakdown, and immunosuppressive therapy 2, 5.
• KDIGO 2021 mandates that all patients receive pneumococcal and seasonal influenza vaccinations as routine preventive care 4.
• Patients receiving high-dose immunosuppression (prednisone, rituximab, cyclophosphamide) should receive prophylactic trimethoprim-sulfamethoxazole 4.

Progressive Kidney Dysfunction

• Proteinuria exceeding 3.8 g/day carries a 35% risk of progression to end-stage renal disease within 2 years, compared with only 4% risk when proteinuria is below 2.0 g/day 1.
• Heavy proteinuria directly injures tubular epithelial cells through protein overload, causing tubular atrophy and interstitial fibrosis 2.
• Proteinuria may trigger formation of cellular or fibrous crescents, leading to rapidly progressive glomerulonephritis or focal glomerulosclerosis 2.
• Acute kidney injury is a recognized complication requiring prompt recognition and management 3.

Cardiovascular and Metabolic Complications

• Each 1.0 g/dL decrease in serum albumin increases mortality odds by 137% and morbidity odds by 89% 1.
• Dyslipidemia is nearly universal, characterized by elevated cholesterol, triglycerides, VLDL, IDL, and apolipoprotein B-containing lipoproteins 6.
• The lipid abnormalities include decreased lipoprotein lipase activity, decreased hepatic lipase activity, increased PCSK9 levels, and impaired HDL maturation with reduced cholesterol efflux 6.
• Dyslipidemia increases atherosclerotic risk, causes direct podocyte dysfunction, and contributes to vascular thrombosis 2, 6.

Edema and Fluid Complications

• Edema formation results from both increased capillary permeability and primary activation of the Na/K pump in the collecting duct 7.
• Sodium retention and edema represent the dominant clinical manifestations requiring active management 7.

Additional Systemic Complications

• Thyroid hormone abnormalities occur due to urinary loss of thyroid-binding proteins 5.
• Oral health complications have been documented in pediatric populations 5.
• Hypogammaglobulinemia from urinary immunoglobulin loss further compounds infection risk 2.

Clinical Pitfalls and Monitoring

A critical caveat: hypoalbuminemia is usually associated with increased mortality and kidney dysfunction, making albumin level a key prognostic marker 2.

Serum albumin measured by bromocresol green (BCG) assays overestimates true albumin compared with bromocresol purple (BCP) assays, potentially affecting thromboembolism risk stratification 1.

The lack of insurance coverage for urine dipsticks in the United States represents a significant barrier to optimal disease monitoring and complication prevention 8.