Human Pathology: General Concepts of Disease and Principles of Diagnosis

Human Pathology: General Concepts of Disease and Principles of Diagnosis

Institution: Georgia Institute of Technology
Instructor: Dr. Adam J. Decker

Learning Objectives

  1. Definitions

    • Common terms used to describe disease, including lesions, symptomatic and asymptomatic disease, etiology, and pathogenesis.

  2. Categories of Disease

    • Major classifications of human disease.

  3. Diagnosis Approach

    • Outline the method a practitioner uses to diagnose and decide on treatment for patients.

  4. Diagnostic Tests

    • Different kinds of tests and procedures that aid in diagnosis.

  5. Imaging Techniques

    • Compare and contrast various imaging techniques described.

Introduction to Pathology

  • Pathology

    • Derived from Greek: "pathos" (disease) + "logos" (treatise).

    • Defined as a study of the structural and functional deviations from the normal that constitute disease or characterize a particular disease.

    • Aberrant: Refers to departure from an accepted standard.

Understanding Disease

  • Disease Components:

    • Etiology: The cause of the disease, which may be idiopathic (unknown cause).

    • Pathogenesis: The cellular events occurring prior to the appearance of clinical signs and symptoms.

    • Morphology: Abnormal anatomy evaluated through radiological, gross, or microscopic/histological examination.

    • Clinical Expression: Signs (measurable or observable) and symptoms (subjective experiences) of the disease.

    • Compliance: Emphasizes the patient's need to comply with treatment regimens.

Homeostasis and Disease

  • A disruption in homeostasis leads to a state of DIS/EASE, highlighting the balance necessary for healthy bodily function.

Historical Context

  • Rudolph Virchow (1821-1902)

    • Known as the Father of Modern Pathology.

    • Asserted that all diseases are caused by visible cell abnormalities.

    • Coined several medical terms including: leukemia, embolism, thrombosis, spina bifida.

Types of Pathology

  • General Pathology: Examines concepts of degeneration, inflammation, and neoplasia (uncontrolled cell division).

  • Systemic Pathology: Assesses the diseases within the 11 organ systems:

    1. Circulatory System

    2. Skeletal System

    3. Respiratory System

    4. Digestive System

    5. Integumentary System

    6. Lymphatic/Immune System

    7. Endocrine System

    8. Reproductive System

    9. Muscular System

    10. Urinary System

    11. Nervous System

Study of Disease

  • Symptoms (Subjective): Experience reported by the patient (e.g., headaches).

  • Signs (Objective): Observable or measurable conditions that indicate disease (e.g., fever).

  • Pathogenesis: The mechanisms that lead to disease.

  • Etiology: The known cause of disease may be classified as:

    • Idiopathic: Unknown cause.

    • Known: Identifiable causative agents.

Signs vs. Symptoms

  • Signs

    • Definition: Objective evidence of disease recognized by others.

    • Examples: Fever, rash, swelling, lab results.

  • Symptoms

    • Definition: Subjective feelings experienced only by the patient.

    • Examples: Pain, fatigue, headaches.

Categories of Signs

  1. Prognostic Signs: Indicate the likely future outcome of a disease (e.g., TNM scale).

  2. Anamnestic Signs: Relate to past medical history (e.g., scarring from past acne).

  3. Diagnostic Signs: Present in the current health problem (e.g., elevated PSA indicates prostate issues).

  4. Pathognomonic Signs: Definitive indicators linking to specific diseases (e.g., certain microbes indicating a specific bacterial infection).

Principles of Diagnosis

  • Diagnosis: Determining the nature and cause of the illness based on:

    • Clinical history

    • Physical examination

    • Differential diagnosis

  • Prognosis: Prediction of the eventual outcome based on diagnosis.

  • Treatment:

    • Specific treatment: Targets the underlying cause.

    • Symptomatic treatment: Aims to alleviate symptoms without affecting the disease course.

Clinical History

  1. Current Illness History: Characterizes the severity, onset time, and nature of symptoms.

  2. Medical History: Explores general health and past illnesses relevant to current issues.

  3. Family History: Health conditions in family members that may impact the patient.

  4. Social History: Information on occupation and lifestyle factors impacting health (e.g., substance use).

  5. Review of Symptoms: Assessment of other symptoms to identify additional affected body areas.

Review of Systems

  • Evaluation of various body parts regarding signs and symptoms, including:

    • Skin: Rashes, itching, hair/nail changes

    • Head: Headaches, injuries

    • Eyes: Vision changes, eye pain

    • Ears: Hearing changes, ear pain

    • Nose/Sinuses: Nosebleeds, allergies

    • Mouth/Throat: Gum issues, sore throat

    • Neck: Lumps, stiffness

    • Breasts: Lumps, pain

    • Respiratory/Cardiac: Breathing issues, heart symptoms

    • Gastrointestinal: Changes in appetite, bowel issues

    • Urinary: Issues with urination

    • Musculoskeletal: Joint issues, pain

    • Neurologic: Headaches, seizures

    • Hematologic: Blood-related issues (e.g., anemia)

    • Endocrine: Growth and metabolic issues

    • Psychiatric: Mental health concerns.

Pain Assessment Techniques

  • Mnemonic OPQRST:

    • O: Onset - when pain started.

    • P: Provocation - factors affecting pain intensity.

    • Q: Quality - description of pain.

    • R: Radiates - pain spreading locations.

    • S: Severity - intensity level.

    • T: Time - duration of pain.

  • Mnemonic SOCRATES: Similar pain assessment attributes with some variation in focus.

Wong-Baker Pain Scale

  • A graphical rating scale used to assess levels of pain from 0 (no pain) to 10 (worst pain).

Medical Abbreviations

  • b.i.d.: twice a day

  • b.i.n.: twice a night

  • bx: biopsy

  • ca: cancer

  • CBC: complete blood count

  • CC: chief complaint

  • CHF: congestive heart failure

  • CIS: carcinoma in situ

  • c/o: complains of

  • COPD: chronic obstructive pulmonary disease

  • CXR: chest x-ray

  • DOA: dead on arrival

  • DOB: date of birth

  • ddx: differential diagnosis

  • dx: diagnosis

  • ED: emergency department

  • FBS: fasting blood sugar

  • FUO: fever of unknown origin

  • h/o: history of

  • HPI: history of present illness

  • hx: history

  • IM: intramuscular

  • IV: intravenous

  • LP: lumbar puncture

  • MI: myocardial infarction

  • MRI: magnetic resonance imaging

  • NGT: nasogastric tube

  • NKA: no known allergies

  • NPO: nothing by mouth

  • O.D.: right eye

  • O.S.: left eye

  • OTC: over the counter

  • p.o.: orally

  • p.r.n.: as needed

  • PSA: prostate specific antigen

  • PT: prothrombin time

  • PTT: partial thromboplastin time

  • q: every

  • q.d.: every day

  • q.h.: every hour

  • q.2h.: every 2 hours

  • q.4h.: every 4 hours

  • q.i.d.: four times a day

  • qns: quantity not sufficient

  • REM: rapid eye movement

  • R/O: ruled out

  • ROM: range of motion

  • ROS: review of systems

  • SOB: shortness of breath

  • Sx: symptoms

  • t.d.s: to be taken three times daily

  • Tx: treatment

  • UA: urinalysis

  • WNL: within normal limits

  • yo: years old

Physical Examination

  • Purpose: A systematic examination of the patient focusing on affected areas, correlating found abnormalities with clinical history.

  • Differential Diagnosis: Thorough consideration of possible diseases or conditions that may cause the observed symptoms and signs, supplemented with laboratory tests or other diagnostics.

Choosing Diagnostic Tests

  • General Considerations:

    • Cost: Evaluation based on affordability.

    • Invasiveness: Assessing whether a test is invasive or noninvasive.

    • Appropriateness: Relating to the clinical questions being addressed.

    • Test Reliability: The ratio of false positives and negatives must be assessed to determine effectiveness.

Screening Tests for Disease

  • Purpose: To detect diseases early, even when asymptomatic, which allows for timely treatment to minimize late-stage damage.

  • Genetic Screening: Identifying carriers of certain genetic conditions to assist in future childbearing decisions.

Effective Screening Requirements

  1. Target Group: A notable number of individuals at risk.

  2. Test Suitability: Tests must be noninvasive, affordable, and with low false-positive/negative rates.

  3. Benefits: The benefits must outweigh any risks/harms.

Examples of Screening Tests

  • Noninvasive:

    • Puff tonometry for glaucoma.

  • Invasive:

    • Colonoscopy for detecting colon polyps and diverticula.

Clinical Laboratory Diagnostic Tests

  • Purpose: Assess concentrations or activity of particular substances altered by diseases in bodily fluids (blood/urine).

  • Uses Include:

    • Evaluating organ function.

    • Monitoring cancer therapy responses.

    • Detecting pathogenic organisms.

    • Assessing responses to medications.

Imaging Diagnostic Tests

X-ray

  • Utilizes high-energy radiation for imaging disease diagnostics.

  • Radiological Terms:

    • Radiopaque: Appears white (high-density tissues).

    • Radiolucent: Appears dark (low-density tissues).

Contrast Media in X-rays

  • Examples of substances used to improve visualization of structures:

    • Barium sulfate: Used for the intestinal tract.

    • Intravenous dye: Used for urinary tract imaging.

Common Imaging Techniques

CT (Computed Tomography)

  • Principle: Radiation detectors measure X-ray absorption; computers reconstruct images.

  • Diagnostic Utility: Assisting in cancer screening and identifying undetected internal organ conditions.

MRI (Magnetic Resonance Imaging)

  • Principle: Produces images using hydrogen protons in a magnetic field.

  • Contrast: Does not utilize ionizing radiation; detects abnormalities in soft tissues.

Cytology and Histology

  • Cytology: Examines abnormal cells in fluids or secretions (e.g., Pap smears).

  • Histology: Involves examining tissue samples for irregular cellular patterns (e.g., biopsies).

Tests for Electrical Activity

  • Types:

    • ECG: Monitors heart's electrical activity throughout the heart cycle.

    • EEG: Measures brain activity.

    • EMG: Evaluates muscle electrical activity.

    • NCV: Tests conduction velocity of nerves.

Additional Diagnostic Tests

Endoscopy

  • Tools utilized to inspect the interior of the body using flexible tubes with lenses.

  • Examples: Bronchoscope (airways), colonoscope (colon), cystoscope (bladder).

Ultrasound

  • Emits high-frequency sound waves to visualize internal organ structures based on echo reflection.

Necrosis: Cell or Tissue Death

  • Defined as cell death due to ischemia (restricted blood flow).

  • Types of Necrosis:

    • Gangrenous: Cell death characterized by serious conditions (wet/dry).

    • Caseous: Cheese-like consistency, often associated with tuberculosis.

    • Fibrinoid: Seen in notables like rheumatoid arthritis.

    • Liquefactive: Tissue transformation into liquid due to infections.

Stages of Somatic Death

  1. Algor Mortis: Cooling of body temperature post-death.

  2. Livor Mortis: Blood pooling leading to skin discoloration.

  3. Rigor Mortis: Post-death muscle stiffness due to chemical changes.

  4. Postmortem Autolysis: Decomposition of tissues after death.

Conclusion

  • Understanding the concepts from etiology to symptoms to diagnosis is crucial for studying human pathology and practicing medicine effectively.