Renal Pathology Lecture Notes

Introduction

• Overview of renal pathology and its importance in understanding kidney diseases.
• Discussion of the basic histology of the kidney, which aids in diagnosing diseases.

Key Components of Renal Tissue

1. Glomerulus
   • Tuft of capillaries that filter blood.
2. Renal Tubules
   • Responsible for reabsorbing substances such as electrolytes.
3. Blood Vessels
4. Interstitium
   • Supports renal tissue, including the two poles.

Clinical Syndromes in Renal Diseases

• Renal diseases exhibit a limited number of symptoms classified into clinical syndromes:
  • Nephrotic syndrome
  • Nephritic syndrome
  • Acute and chronic renal failure.

Importance of Knowledge in Diagnosis

• Understanding normal kidney structure and functions is crucial in diagnosing renal diseases.
• Correlation of light microscopy findings with immunofluorescence and electron microscopy is important, though only light microscopy will be observed in the pre-lab.

Glomerulus Structure

• Vascular structure composed of specialized fenestrated capillaries.
• Capillaries arranged in lobules and supported by a mesangium.
• Bowman's space is the lumen surrounding the capillaries, lined by simple squamous epithelial cells.
• Podocytes: Epithelial cells with tiny foot processes, seen on electron microscopy.

Hydropic Change of the Kidney

• Definition: Reversible cell injury due to toxic damage.
• Characterized by swollen renal tubules and accumulation of water inside the cells.
• Reversible injury: nucleus is present with no necrosis features such as karyolysis.

Acute Kidney Infarct

• Occurs when blood supply is diminished or cut off.
• Commonly due to embolism, often from myocardial infarction.
• Classification: White infarcts due to arterial occlusion.
• Microscopic Features: Coagulative necrosis, preserved architecture, hypodemic areas due to congestion, absence of nuclei, and increased eosinophilia.

Acute Glomerulonephritis (Post-Streptococcal)

• Characterized by diffuse endocapillary proliferation of glomerular cells due to immune complex deposition (type 3 hypersensitivity).
• Common symptoms: hematuria, proteinuria, azotemia, hypertension.
• Microscopic Features: Hypercellularity of glomeruli due to inflammatory cell infiltration and mesangial proliferation.
• Immunofluorescence: Granular appearance of IgG and C3 deposits.
• Electron Microscopy: Sub-epithelial electron dense deposits (humps).

Goodpasture Syndrome

• An autoimmune disease with autoantibodies against the glomerular basement membrane.
• Can also affect the lungs (pulmonary symptoms, hemoptysis).
• Microscopic Features: Crescent formation within Bowman's space; proliferation of epithelial cells and macrophage infiltration.
• Staining: Linear deposition of IgG and C3 along the basement membrane.

Membranous Nephropathy

• Most common cause of nephrotic syndrome in adults, characterized by diffuse glomerular wall thickening.
• Caused by immune complex deposition on the sub-epithelial side of the basement membrane.
• Symptoms: heavy proteinuria, hypoproteinemia, edema, hypertension.
• Microscopic Features: Absence of hypercellularity and inflammatory cells, thickened capillary walls.
• Immunofluorescence: Granular appearance of immunoglobulins and complement.
• Electron Microscopy: Sub-epithelial deposits with spikes (due to basement membrane deposits).

Membranoproliferative Glomerulonephritis (MPGN)

• Characterized by hypercellularity due to mesangial activation and infiltration of inflammatory cells.
• Microscopic Features: Double contour/tram track appearance of the basement membrane.

IgA Nephropathy (Berger's Disease)

• Most common cause of glomerulonephritis worldwide.
• Characterized by IgA deposits in mesangial regions, leading to mesangial proliferation.
• Symptoms: Hematuria following infections in the respiratory or gastrointestinal tract.
• Microscopic Features: Glomerular hypercellularity and hyalinosis in the mesangium.
• Immunofluorescence: Mesangial deposition of IgA and C3.