The Concepts of Renal Failure · 3 min read
Glomerulosclerosis
Definition and Pathophysiology
Glomerulosclerosis refers to scarring and hardening of the glomeruli due to accumulation of extracellular matrix proteins. This progressive condition leads to obliteration of glomerular capillaries and loss of filtration surface area.
The pathological process begins with injury to glomerular cells, particularly podocytes and endothelial cells. Injured cells release cytokines and growth factors that stimulate mesangial cell proliferation and matrix production. Transforming growth factor-beta (TGF-β) plays a central role in promoting fibrosis.
Hemodynamic factors contribute to glomerulosclerosis. Glomerular hypertension and hyperfiltration increase mechanical stress on remaining nephrons after initial injury. This adaptive hyperfiltration initially maintains GFR but ultimately accelerates glomerular damage.
Types of Glomerulosclerosis
Focal segmental glomerulosclerosis (FSGS) affects some glomeruli (focal) and portions of affected glomeruli (segmental). Primary FSGS results from podocyte injury of unknown etiology. Secondary FSGS occurs in response to conditions causing glomerular hyperfiltration, including obesity, unilateral renal agenesis, reflux nephropathy, and previous glomerular disease.
Global glomerulosclerosis involves the entire glomerular tuft. This pattern typically represents end-stage scarring from various glomerular diseases.
Nodular glomerulosclerosis (Kimmelstiel-Wilson nodules) is characteristic of diabetic nephropathy. Eosinophilic nodules form within the mesangium due to accumulation of glycosylated matrix proteins.
Clinical Manifestations
Proteinuria is the hallmark of glomerulosclerosis. Damage to the glomerular filtration barrier allows protein leakage into urine. Nephrotic-range proteinuria exceeds 3.5 grams per 24 hours and indicates severe glomerular injury.
Hypertension develops as the RAAS activates in response to decreased renal perfusion. Sodium and water retention contribute to volume-dependent hypertension.
Edema results from hypoalbuminemia secondary to urinary protein losses. Decreased oncotic pressure allows fluid to shift from the intravascular to interstitial compartment.
Hyperlipidemia occurs as the liver increases lipoprotein synthesis in response to decreased oncotic pressure. Total cholesterol, LDL, and triglycerides are typically elevated.
Progressive decline in GFR leads to uremia if the underlying process is not controlled.
Risk Factors
Hypertension causes glomerular capillary hypertension and accelerates sclerosis. Target blood pressure for patients with proteinuric kidney disease is less than 130/80 mmHg.
Diabetes mellitus promotes glomerulosclerosis through glycosylation of basement membrane proteins, generation of reactive oxygen species, and activation of protein kinase C pathways.
Obesity causes hyperfiltration and glomerular hypertension. Weight loss may slow progression of glomerulosclerosis in obese patients.
African American race is associated with higher incidence and faster progression of FSGS. Genetic variants in APOL1 contribute to this increased risk.
Advanced age is associated with gradual loss of nephrons and increased prevalence of glomerulosclerosis.
Management Principles
Blood pressure control with ACE inhibitors or angiotensin receptor blockers (ARBs) reduces glomerular capillary pressure and slows progression. These agents also have direct anti-proteinuric and anti-fibrotic effects.
Dietary protein restriction to 0.8 g/kg/day may reduce hyperfiltration and proteinuria.
Sodium restriction to less than 2 grams daily helps control hypertension and edema.
Lipid-lowering therapy with statins reduces cardiovascular risk and may have renoprotective effects.
Immunosuppressive therapy may be considered for primary FSGS refractory to supportive measures. Options include corticosteroids, calcineurin inhibitors, and mycophenolate mofetil.
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