Glomerulonephropathies

Nephrotic Syndrome

Introduction:

The nephrotic syndrome is a clinical syndrome defined as marked proteinuria (> 3.5/day), hypoalbuminemia, ascites or edema, and hypercholesterolemia. It usually occurs secondary to glomerulonephritis or amyloidosis.

Pathophysiology:

Injured glomeruli cause massive protein leakage into the urine. Hypoproteinemia results due to excessive protein loss without adequate protein synthesis for replacement. Edema or ascites is caused by decreased plasma oncotic pressure and increased aldosterone activity, causing sodium retention. The hypercholesterolemia is due to the decreased catabolism of proteins and lipoproteins and increased synthesis of proteins and cholesterol by the liver. The smaller molecular weight proteins, such as albumin and antithrombin III, are lost via the damaged glomeruli, but the larger molecular weight, cholesterol-rich lipoproteins accumulate.

 

Histopathology:

The glomerular basement membrane permeability to albumin is increased but the glomerulus appears normal by light microscopy.

 

Clinical signs:

  • Generalized edema

  • Ascites

  • Pleural effusion

  • Depression

  • Anorexia, weight loss, muscle wasting

  • Nausea, vomiting

Clinical Pathology:

  •   Severe proteinuria

  • · Hypoproteinemia

  • · Edema and/or ascites

  • · Hyperlipidemia

  • · Thromboembolism

 

 

Complications:

 

Hypertension and hypercoagulability are frequent complications. The hypertension is due to sodium retention, increased activation of the renin-angiotensin system, scarring of glomerular vessels, low production of renal vasodilators, and increased response to pressor mechanisms. Hypercoagulability and thromboembolisms (such as a saddle thrombus) occur due to the loss of antithrombin III, which normally modulates fibrin and thrombin production. Antithrombin III and heparin inhibits clotting factors II, IX, X, XI, and XII. Mild thrombocytosis, increased platelet adhesion and aggregation may result.

 

More information:

Nelson, R.W., Couto, C.G., et al. 1998. The nephrotic syndrome. In: Small Animal Internal Medicine. Mosby pp. 609-611.

Tilley, L.P., and Smith, F.W. 2000. The nephrotic syndrome. In: The Five Minute Veterinary Consult Canine and Feline. Williams and Wilkins pp.874-875.

Pubmed search:

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