Pathology and Disease Diagnosis

Pathology

• The study of disease.
• Pathologists are involved in diagnostics, performing necropsies, biopsies, toxicological evaluations, clinical testing, and experimental studies of the underlying mechanisms of disease.

Pathogenesis

• The development of disease from its initial stages to its cellular and molecular manifestations.

Disease Diagnosis

• Case history, symptoms, and clinical signs are important in diagnosis.
• Analysis of blood and body fluids, biopsies, and necropsies are key components of disease diagnosis.
• Microscopic lesions, ultrastructural changes, and etiologic identification contribute to diagnosis.
• Treatment and prognosis, which is the expected outcome of the disease, are also considered.
• Prevention and control measures include hygienic practices and vaccinations.

Types of Diagnosis

• Clinical diagnosis relies on case history, clinical signs, and physical examinations.
• Clinical pathologic diagnosis is based on changes observed in the chemistry of bodily fluids, hematology, cell structure, and function.
• Morphological diagnosis involves macroscopic ("gross") or microscopic ("histologic") observations, describing severity, duration, distribution, location, and nature.
• Etiological diagnosis pinpoints the specific cause of the disease.

Prognosis

• Excellent, good, guarded, and grave are common categories used to describe the anticipated course of a disease.

Detecting Morphologic Changes

• Gross examination includes both physical examination of living animals and postmortem examination of deceased animals.
• Microscopic examination uses both light and electron microscopy.
• Advanced techniques involve specialized microscopes, laser capture microdissection, DNA microarrays, and proteomics.

Cell Injury

• Cell injury can occur due to:
  • Oxygen deficiency
  • Physical agents
  • Infectious agents
  • Nutritional deficiencies
  • Genetic abnormalities
  • Workload imbalances
  • Chemical exposures, drugs, or toxins
  • Immunological dysfunction
  • Aging

Cellular Responses to Injury

• Injury can cause three cellular responses:
  • Adaptation (with or without accumulations or degenerative changes)
  • Reversible cell injury (with or without subcellular changes)
  • Irreversible cell injury (Death), which results in necrosis.