1. Chapter 1
General Concepts of Disease:
Principles of Diagnosis

2. Learning Objectives Define: Categories of human disease
Lesions
Organic and functional disease
Symptomatic and asymptomatic disease
Etiology
Pathogenesis
Categories of human disease
Types of diagnostic tests and procedures

3. Characteristics of Disease (1 of 3)
Disease: disturbance of body structure or function
Lesions: well-defined, characteristic structural changes in organs and tissues as a result of disease
Organic disease
Associated with structural changes
Gross examination
Histologic examination
Functional disease
No morphological abnormalities yet body functions are profoundly disturbed

4. Characteristics of Disease (2 of 3)
Pathology: study of disease
Pathologist: physician who specializes in diagnosing and classifying diseases by studying the morphology of cells and tissues
Clinician: physician/health care professional that cares for patients
Symptoms: subjective manifestations such as pain or weakness
Signs: physical findings or objective manifestations such as swelling or redness

5. Characteristics of Disease (3 of 3)
Symptomatic disease: with symptoms and/or signs
Asymptomatic disease: no signs or symptoms
Distinction between asymptomatic and symptomatic depends on extent
Early stages of disease, usually asymptomatic
If not treated, progresses to symptomatic
Etiology: cause of disease
Etiologic agent: agent responsible for causing disease
Pathogenesis: process of development of disease
Pathogen: any microorganism that causes disease

6. Classifications of Disease (1 of 3)
Congenital and hereditary diseases
Developmental disturbances
Causes: genetic abnormalities; abnormalities in chromosome number or distribution; intrauterine injury; interaction of genetic and environmental factors
Hemophilia (hereditary), German measles (congenital)

7. Classifications of Disease (2 of 3)
Inflammatory diseases: Body reacts to injury through an inflammatory process
Bacteria or microbiologic agents: sore throat
Allergic reaction: hay fever
Autoimmune diseases: SLE, diabetes type 1
Unknown etiology
Degenerative diseases
Tissue or organ degeneration as a result of aging or breakdown
Arthritis, atherosclerosis

8. Classifications of Disease (3 of 3)
Metabolic diseases: Disturbance in metabolic process in body
Diabetes, hyper- or hypothyroidism, fluid and electrolyte imbalance
Neoplastic diseases: Uncontrolled cell growth
Benign: lipoma
Malignant: Lung cancer
Basis of classification
1. Similarity of lesions
2. Similarity of pathogenesis
Diseases with similarities may not necessarily be closely related

9. Health and Disease
WHO (1948) – wellness is the complete state of physical, mental and social well-being and not simply the absence of disease and infirmity.
Good health: more than the absence of disease
Condition in which body and mind function efficiently and harmoniously as an integrated unit
Traditional medicine: goal is to cure or ameliorate disease.
Modern medicine: advances relieve suffering and advance human welfare but do not guarantee good health.

10. Contrast to Homeopathic medicine Preventive medicine Pharmaceutical
Allopathic medicine- usually refers to traditional western medicine -
The term allopathy was coined by the founder of homeopathy, Samuel Hahnemann, to differentiate homeopathic practices from conventional medicine of the day, based on the types of treatments used. Hahnemann used allopathy to refer to what he saw as a system of medicine that combats disease by using remedies that produce effects in a healthy subject that are different (hence Greek root allo- "different") from the effects produced by the disease to be treated.
Contrast to Homeopathic medicine
Preventive medicine
Pharmaceutical
Neutraceutical

11. Homeopathy is a form of alternative medicine in which practitioners use highly diluted preparations. Homeopathy was first proposed by German physician Samuel Hahnemann in 1796, based on an ipse dixit axiom formulated by Hahnemann, which he called the law of similars, preparations which cause certain symptoms in healthy individuals are given to patients who already exhibit similar symptoms.

12. Preventive medicine or preventive care refers to measures taken to prevent diseases, (or injuries) rather than curing them or treating their symptoms. The term contrasts in method with curative and palliative medicine, and in scope with public health methods (which work at the level of population health rather than individual health).

13. A pharmaceutical drug, also referred to as medicine or medication, can be loosely defined as any chemical substance intended for use in the medical diagnosis, cure, treatment, or prevention of disease
Nutraceutical, a term combining the words “nutrition” and “pharmaceutical”, is a food or food product that provides health and medical benefits, including the prevention and treatment of disease.
Nutraceutical products may range from isolated nutrients, dietary supplements and specific diets to genetically engineered foods, herbal products, and processed foods such as cereals, soups, and beverages

14. Continuum of Health and Disease
Good Health
Serious Illness
Everyone is somewhere between the midpoint and good health
Good health requires active participation, assuming responsibility for one’s health
Eat properly, exercise, avoid harmful excesses such as overeating, smoking, heavy drinking, or using drugs
Use one’s mind constructively, express emotions appropriately, nurture a positive mental attitude

15. Principles of Diagnosis
Diagnosis: determination of nature and cause of illness
Clinical history
Physical examination
Differential diagnosis
Prognosis: eventual outcome of disease
Treatment
Specific treatment – directed at underlying cause
Symptomatic treatment – alleviates symptoms but does not influence course of disease

16. Clinical History (1 of 2) 1. History of current illness
Severity, time of onset, and character of patient’s symptoms
2. Medical history
Details of general health and previous illnesses that may shed light on current problems
3. Family history
Health of patient’s parents and family members; diseases that run in families

17. Clinical History (2 of 2) 4. Social history 5. Review of symptoms
Patient’s occupation, habits, alcohol and tobacco consumption, general health, current problems
5. Review of symptoms
Symptoms other than disclosed in history of present illness, suggesting other parts of the body affected by disease

18. Physical Examination Physical examination Differential diagnosis
Systematic examination of patient, with emphasis on parts of body affected by illness
Abnormalities noted correlated with clinical history
Differential diagnosis
Consideration of various diseases or conditions that may also explain patient’s symptoms and signs
Diagnostic possibilities narrowed by selected laboratory tests or other diagnostic procedures
Opinion of medical consultant may be sought

19. Screening Tests Screening tests for detection of disease
Detect early asymptomatic diseases amenable to treatment to prevent or minimize late-stage organ damage
Screening for some genetic diseases
To screen for carriers of some genetic diseases transmitted from parent to child as either dominant or recessive trait
Identifying carriers allows affected persons to make decisions on future childbearing or management of current pregnancy
Example: recessive gene for sickle cell anemia in 8% of Black population

20. Requirements for Effective Screening
A significant number of persons must be at risk for the disease in the group being screened.
A relatively inexpensive noninvasive test must be available to screen for the disease that does not yield a high number of false-positive or false-negative results
Early identification and treatment of the disease will favorably influence course of disease.

21. Examples of Screening Tests
PPD - For TB
PSA – Prostate Specific Antigen – For Prostate Cancer
Alpha Fetoprotein – screening to detect certain fetal abnormalities
Mammogram and BRAC to detect breast cancer
Pap Smear for cervical cancer
Colonoscopy for Colon Cancer
Blood Sugar test for diabetes
Blood Pressure Determination for Hypertension

22. Diagnostic Tests and Procedures (1 of 13)
Clinical laboratory tests
Purpose: To determine concentration of substances in blood or urine frequently altered by disease
Uses:
Determine concentration or activity of enzymes in the blood
Evaluate function of organs
Monitor response of certain cancers to treatment
Detect disease-producing organisms in urine, blood, feces
Determine response to antibiotics

23. Lab Tests

24. Lab Tests

25. Lab Tests

26. Diagnostic Tests and Procedures (2 of 13)
Tests of electrical activity: to measure electrical impulses associated with bodily functions and activities
ECG: measures serial changes in electrical activity of the heart in various phases of the cardiac cycle
Identify disturbances in heart rate, rhythm, abnormal impulses
Recognize heart muscle injury from ECG abnormalities
EEG: measures electrical activity of brain; brain waves
EMG: measures electrical activity of skeletal muscle during contraction and at rest

27. Diagnostic Tests and Procedures (3 of 13)
Radioisotope (radionuclide) studies: evaluate organ function by determining rate of uptake and excretion of substances labeled with a radioisotope
Uses:
Anemia: radioisotope-labeled vitamin B12
Hyperthyroidism: radioactive iodine
Pulmonary blood flow: albumin; to detect presence of blood clots
Cancer spread: phosphorus; to determine presence of tumor deposits in bone or spine
Heart muscle damage: evaluate blood flow

28. Diagnostic Tests and Procedures (4 of 13)
Endoscopy
To examine interior of body using rigid or flexible tubular instruments equipped with lens and light source
To perform surgery formerly done through large abdominal incisions
Bronchoscope: trachea and major bronchi
Cystoscope: bladder
Laparoscope: abdomen
Ultrasound
Mapping echoes produced by high-frequency sound waves transmitted into body; echoes reflect change in tissue density, producing images

29. Diagnostic Tests and Procedures (5 of 13)
X-ray
Principle: use of high-energy radiation waves at lower doses to produce images to help diagnose disease
Can penetrate through tissues at varying degrees depending on tissue density
Act on a photographic film or plate (roentgenogram) as the rays leave the body
Radiopaque: appears white on film; high-density tissues such as bone absorb most of the rays
Radiolucent: appears dark on film; low-density tissues allow rays to pass through

30. Diagnostic Tests and Procedures (6 of 13)
X-ray can include use of contrast media to outline structures not otherwise visualized on standard films
Barium sulfate: intestinal tract
Radiopaque oil: bronchogram
Intravenous dye: intravenous pyelogram; urinary tract
Radiopaque tablets: visualize gallstones
Arteriogram: visualize blood flow, identfy narrowing or obstruction
Cardiac catherization: blood flow through heart, detect abnormal communications between chambers

31. Diagnostic Tests and Procedures (7 of 13)
Computed tomographic (CT) scans
Principle: radiation detectors record amount of X-rays or ionizing radiation absorbed by body and feed data into a computer that reconstructs the data into an image
Radiopaque and radiolucent tissues appear white and dark as in a conventional x-ray
Individual organs sharply demarcated by planes of fat that appear dark because of its low density
Delivers higher dose of ionizing radiation than x-ray

32. Diagnostic Tests and Procedures (8 of 13)
Uses of computed tomographic (CT) scans
Cancer screening asymptomatic individuals
Detect abnormalities in internal organs that cannot otherwise be identified by standard x-ray

33. Diagnostic Tests and Procedures (9 of 13)
Magnetic resonance imaging (MRI)
Principle: computer-constructed images of body based on response of hydrogen protons in water molecules when placed in a strong magnetic field
Protons align in the direction of the magnetic field
Protons are temporarily dislodged and wobble when radiofrequency waves are directed at them
Protons emit a measurable signal (resonance) that can be used to construct images
Intensity of resonance depends on water content of tissues, strength and duration of radiofrequency pulse

34. Diagnostic Tests and Procedures (10 of 13)
MRI: advantages over CT scan
Does not use ionizing radiation
Can detect abnormalities in tissues surrounded by bone, such as spinal cord, orbit, skull
Bone interferes with scanning because of its density but does not produce an image in MRI because of its low water content
Uses
Multiple sclerosis
Superior to mammography in detecting breast cancer

35. Diagnostic Tests and Procedures (11 of 13)
Positron emission tomography (PET)
Principle: Measures metabolism of biochemical compounds that are labeled with positron-emitting isotopes to measure organ function, example glucose
Disadvantages
Very expensive and not widely available
Requires facilities for incorporating the isotopes into the biochemical compound

36. Diagnostic Tests and Procedures (12 of 13)
Uses of PET
Assess biochemical functions in brain
Determine metabolic activities of organ or tissue; specific site in an organ where compound is metabolized
Evaluate changes in blood flow in heart muscle following a heart attack
Distinguish benign from a malignant tumor (increased glucose uptake in malignant versus benign tumors)

37. Diagnostic Tests and Procedures (13 of 13)
Cytologic and histologic examinations
Papanicolau (Pap) smear: identifies abnormal cells in fluids or secretions; for recognizing early changes that may be associated with cervical and other cancers
Biopsy: tissue samples obtained for histologic examination to determine abnormal structural and cellular patterns accompanying disease
Liver, kidney, bone marrow

38. Radioisotope bone scan of head, chest, and pelvis
© Courtesy of Leonard Crowley, M.D./University of Minnesota Medical School

39. Ultrasound examination of 22-week-old fetus
Courtesy of Belinda Thresher

40. X-ray of colon with radiopaque barium sulfate
© Courtesy of Leonard Crowley, M.D./University of Minnesota Medical School

41. Bronchogram showing normal caliber and branching of bronchi and bronchioles
© Courtesy of Leonard Crowley, M.D./University of Minnesota Medical School

42. IVP showing large cyst, right kidney
© Courtesy of Leonard Crowley, M.D./University of Minnesota Medical School

43. Opened gallbladder, same patient
X-ray of gallbladder; gallstones appear as radiolucent (dark) within a radiopaque bile (white)
Opened gallbladder, same patient
© Courtesy of Leonard Crowley, M.D./University of Minnesota Medical School

44. Carotid angiogram, narrowing of carotid artery
© Courtesy of Leonard Crowley, M.D./University of Minnesota Medical School

45. Computed tomographic scan, CT scan
© Courtesy of Leonard Crowley, M.D./University of Minnesota Medical School

46. CT scan, chest, white nodule on left lung indicates tumor
© Courtesy of Leonard Crowley, M.D./University of Minnesota Medical School

47. CT scan, abdomen at level of kidneys, fluid-filled cysts, right kidney
© Courtesy of Leonard Crowley, M.D./University of Minnesota Medical School

48. MRI, brain, with malformation within brain stem
© Courtesy of Leonard Crowley, M.D./University of Minnesota Medical School

49. Discussion
What are the underlying principles for these diagnostic procedures: x-ray, CT scan, MRI, PET?
Explain the requirements for an effective screening.
Differentiate:
Symptomatic versus specific treatment
Sign versus symptom
Symptomatic versus asymptomatic disease
Diagnosis versus prognosis