Fatty Liver Pathology

Fatty Change (Steatosis)

• Accumulation of neutral fat (triglycerides) in cytoplasm of parenchymal cells, commonly occurring in liver, but also in heart, skeletal muscle, and kidneys.
• Causes include hypoxia, bacterial toxins, and chemical agents such as alcohol, phosphorus, and carbon trichloride.
• Fatty liver is caused by increased fatty acid entry, increased fatty acid synthesis, decreased oxidation of fatty acids, and increased esterification of fatty acids.

Pathogenesis of Fatty Liver

• Hypoxic or toxic cell injury leads to diminished enzyme activity, resulting in failure to metabolize fat and subsequent intracellular fat accumulation.

Microscopic Picture of Fatty Liver

• Cells appear swollen with multiple tiny cytoplasmic vacuoles (fat globules) around the nucleus.
• Fat globules fuse together, forming a large globule that pushes the nucleus against the cell membrane, giving a signet ring appearance.

Extracellular Depositions

Urate Deposition (Gout)

• Definition: disturbance in purine metabolism with urate deposition in tissues.
• Causes: primary hereditary hyperuricemia, failure of uric acid elimination in renal diseases, and disturbances of purine metabolism.
• Pathogenesis: hyperuricemia leads to deposition of urate crystals (tophi) in tissues, mainly in joints.

Morphology of Urate Deposition

• Gross: white plaques of urate deposits.
• Microsc.: homogeneous mass (tophi) of urate crystals surrounded by inflammatory reaction with foreign body giant cells.

Amyloid Deposition (Amyloidosis)

• Definition: deposition of amyloid proteins in tissues.
• Composition: amyloid fibrils composed of protein aggregates.
• Chemical classification: based on the type of protein aggregated.

Calcification

• Definition: deposition of calcium salts in sites other than bones and teeth.
• Gross: the calcified tissue appears chalky white and hard.
• Microsc.: calcification appears as blue granules with H&E.

Types of Calcification

• Dystrophic calcification: occurs in dead or dying tissues.
• Metastatic calcification: occurs in normal tissues due to hypercalcemia.

Gangrene

• Definition: massive tissue necrosis followed by putrefaction caused by bacterial activity.
• Risk factors: any factor resulting in cut-off blood supply to the affected part.

Types of Gangrene

• Dry gangrene: gangrene without tissue edema due to evaporation of fluids and drainage through veins and lymphatics of the exposed parts of the body.
• Moist gangrene: gangrene with severe tissue edema and swelling.

Dry Gangrene

• Caused by: gradual arterial occlusion with normal venous and lymphatic drainage.
• Pathological features:
• Area distal to occlusion appears pale and cold due to ischemia.
• Then, it becomes red due to escape of blood from necrotic vessels.
• Lastly, it becomes black.
• Line of demarcation: acute inflammatory zone between
• Grossly: the affected part is dry, shrunken, and dark black, resembling the foot of a mummy.