INTRODUCTION TO

GENERAL PATHOLOGY
VPM 152

Web Review

Paul Hanna Jan 2016

 http://people.upei.ca/hanna
Lecture & Lab handouts, PPT’s, etc

Dr Chelsea Martin’s moodle page

Guidelines / Course Objectives

Schedule / Calendar
Lecturers

Dr Paul Hanna

Dr Shannon Martinson

Dr Chelsea Martin
(course coordinator) Dr Enrique Aburto
Laboratory Instructors

Dr. Andrea Bourque Dr Maria Forzan

Lectures and Laboratories

• 2 lectures / week (Tues 8:30, Fri 9:30)

 Lec Rm “C”

• 1 laboratory / week (Fri 10:30-12:20)

 1 hr. in histopathology lecture room (Lec Rm “C”)
 1 hr. in postmortem demonstration room (1034N)
- note: lab coats and plastic gloves (mandatory)

Friday Jan 8th – Necropsy Demonstration Lab (1034N)

½ Class from 10:30 – 11:20

½ Class from 11:30 – 12:20

[Remember lab coats and gloves]

Course Sections

• Introduction (1)

• Cell Adaptation / Injury / Death (6)

• Circulatory Disturbances (5)

• Inflammation / Repair (9)

• Disturbances of Growth / Neoplasia (6)

Course Goals and Objectives

1. Introduce the subject of Veterinary Pathology

2. Learn and use medical terminology

3. Distinguish normal (& artifacts) from abnormal (pathology)

4. Understand basic disease processes

5. Relate clinical disease manifestations to underlying biochemical

and morphological abnormalities

6. Recognize and describe gross and microscopic changes

7. Make morphologic diagnoses

8. Understand the pathogenesis of specific diseases

Evaluations

Mid-Term Examination 23 Feb 2016

 ~ 30% final grade

Laboratory Examination 15 April 2016

 ~ 30% final grade

Final Examination 27 April 2016

 ~ 40% final grade
 Recommended text

Note, new edition due out this year

Reference
Texts
 http://people.upei.ca/hanna
Websites
http://people.upei.ca/smartinson

http://people.upei.ca/eaburto

Dr Martin’s material on Moodle

http://w3.vet.cornell.edu/nst/ www.merckvetmanual.com
I. Definitions and Terminology
Disease
= a disorder of structure or function, especially one that produces specific clinical
signs

Diaphragmatic hernia, dog. Note stomach & liver in thoracic cavity which would undoubtedly
cause compromised respiration (dyspnea) and likely circulatory and/or GI dysfunction.
Pathology
= the study of disease

= study of the functional, biochemical and morphological alterations in cells,

tissues and organs that underlie disease

Perioral vesicles (small blisters) and erosions Bulla (large blister) on snout of pig with ‘foot-
/ ulcers / crusts on lips (ruptured blisters with and-mouth disease’. You will learn in later
scab formation) in human with “cold sores” courses how certain viruses can damage the
skin with resultant blister formation.
 General Pathology
• the study of the basic reactions of cells and tissues to abnormal stimuli that
underlie all diseases

Systemic Pathology
• the study of the specific responses of specialized organs and tissues to
pathologic stimuli

Sagital section of lumbar vertebral column, pig. Infection / inflammation of a lumbar vertebra body (ie osteomyelitis) which
has resulted in a fracture (ie ‘pathologic fracture’) with dorsal protrustion into the vertebral canal with compression of the
spinal cord (ie compressive myelopathy). What effect would this have on the spinal cord? What clinical signs would you
expect in the pig?
Four aspects of disease form the core of pathology:

 Etiology
• the cause of disease (genetic vs acquired)

 Pathogenesis
• the mechanism or sequence of events leading from initiation of cell or tissue
injury to disease development

 Morphologic Changes
• the structural alterations in cells or tissues that are often characteristic
of the disease

 Clinical significance
• the nature of the morphologic changes and their distribution in tissues
determine the clinical signs and course of the disease
 Lesion
= any structural (or functional) abnormality in an organ, tissue or cell

Fortunately, the malignant form of melanoma

Small melanocytomas (ie benign melanomas) are (ie ‘maligant melanoma’) is much less
common lesions in the perineal region of aging common. Note marked expansion and
grey-white horses. distortion of the tissues.
 Pathognomonic
= a lesion or sign that is specifically distinctive or characteristic of a disease

The classic “bullseye” or “target” rash (erythema

chronicum migrans) seen in ~80% of the cases
of Lyme disease. It is a manifestation of the a
local skin infection at the site where the tick
attached, which typically begins 3 to 30 days after
the bite. While not present in every case of Lyme
disease, when it is seen, it is highly specific (ie
pathognomonic) for this disease.

Note, most pathologists are sticklers for accurate

‘Diamond skin disease’, pig. Most consider this lesion to be
use of terminology and are wary of the term
pathognomonic for infection by the bacterium Erysipelothrix rhusiopathiae;
pathognomonic. For example ringworm lesions in
however there have been a few reports of similar lesions caused by
humans can sometimes be mistaken for erythema
Actinobacillus suis. So again while some lesions can be highly suggestive
migrans.
of a particular etiologic agent, be wary when using the term
‘pathognomonic’ to mean 100% accuracy.
Necropsy (Autopsy)
• postmortem examination of the body to determine the nature of
pathological processes that contributed to death or disease

Abomasal volvulus, cow. The abomasum is displaced dorsal to the right and undergone rotation about its supporting
axis (ie volvulus). In addition to affecting GI function, the rotation compresses the supplying blood vessels and with
arterial pressure being higher than venous pressure, blood continues to get into abomasum, yet has difficulty leaving 
note dark red color of distended abomasum (this is an example of ‘venous infarction’)
Biopsy
= the removal & examination of tissue from the living body to establish a precise diagnosis

http://veterinarymedicine.dvm360.com/ http://veterinarymedicine.dvm360.com/

http://veterinarymedicine.dvm360.com/ http://veterinarymedicine.dvm360.com/

Biopsies of the skin are routinely done in veterinary practice; typically with a 6 mm biopsy ‘punch’ (essentially a ‘cookie
cutter-like’ razor blade). Biopsies of lymph nodes, liver, kidney, gut, spleen are also frequently performed.
Diagnosis (Dx)
= a concise statement or conclusion concerning the nature, cause or name of a
disease process

 Differential Dx
• a list of disease diagnoses that could account for the clinical signs or lesions
in a case

 Clinical Dx
• a diagnosis based on the data obtained from the case history, clinical signs
and physical examination
 Morphologic Dx
• a diagnosis based on the predominant lesion(s) in the tissues

 Etiologic Dx
• a diagnosis that names the cause of the disease

 Disease (Definitive) Dx
• a specific diagnosis that states the “name of the disease”
EXAMPLE:
- 8 month-old pup presented to vet clinic with severe bloody diarrhea of 2 days duration
- puppy died prior to complete clinical work up; necropsy performed

1. Clinical Diagnosis.............................. Hemorrhagic diarrhea

 note: loss of entrocytes lining villi & crypts

2. Morphologic Dx .... Severe, acute, diffuse, necrohemorrhagic enteritis

3. Etiologic Diagnosis.........................… Parvoviral enteritis

4. Disease Diagnosis...........................… Canine Parvovirus

EXAMPLE:

- 4 yr-old dairy cow with a history of chronic diarrhea and emaciation

www.nd.gov/ndda/JohnesInAction.jpg

www.vetnext.com/fotos/cowjohn1.jpg

1. Clinical Diagnosis.............................. Chronic diarrhea / emaciation

 Normal control

Note
thickened
Normal ileum
control from
affected
cow

Note expansion of lamina propria with inflammatory

cells

2. Morphologic Dx .... Severe, chronic, segmental, granulomatous enteritis

Higher magnification with acid fast staining – large numbers of inflammatory cells, predominately macrophages and
giant cells (ie granulomatous inflammation) which contain acid fast bacilli, are expanding the lamina propria

3. Etiologic Diagnosis....................… Mycobacterial enteritis

4. Disease Diagnosis.....................… Johne’s Disease (Paratuberculosis)
II. Who are Pathologists?

 Morphologic (Anatomic) Pathologist

• study morphologic manifestations of disease

Clinical Pathologists
• laboratory analysis of disease in living patients

 Veterinary Pathologists
• mammalian, avian, zoo / wildlife, lab animals / primates, fish

Medical Pathologists
• humans

Comparative Pathologists
• animal models of human disease
II. Who are Pathologists?

 Diagnostic Pathologists
• necropsy and surgical biopsies

Experimental Pathologists
• research on pathology of infectious disease, oncology, etc

Molecular Pathologists
• study of the molecular / genetic basis of disease

Toxicologic Pathologists
• study changes elicited by chemical, pharmacological & environmental agents
 II. Who are Pathologists?

 Special System Pathology

• Neuropathologists

• Dermatopathologists

• Respiratory pathologists

• Ophthalmic pathologists

• Etc
III. Descriptions in Gross Pathology

1. No interpretation should appear in descriptions

2. Description should be:  concise

 grammatically correct
 anatomically precise

3. Minimize comparative references to food or sports equipment

4. Avoid making a description based on a preconceived diagnosis

 OBSERVE carefully
 DESCRIBE completely
 DIAGNOSE (DEDUCE or INTERPRET) confidently
5. Components of a description:

 TISSUE..……………..…. identify the organ or structure

 NUMBER .....………..…. number of lesions present

 DISTRIBUTION…….….. focal, multifocal, locally-extensive, diffuse

 SHAPE………………..... spherical, rectangular, symmetrical, etc

 COLOUR ......….…….… no unusual color terms

 SIZE...………………….... metric  dimensions, vol., weight, % organ involved

 PATTERN .....…………… zonal, reticulated, mottled / variegated

 CONSISTENCY ..….…... soft, firm, hard, fluctuant

 SPECIAL FEATURES…. polypoid (sessile vs pedunculated), papillated etc

 Other: odor, surface appearance, etc

6. Must know the normal before you can recognize the abnormal!

Normal brain (dorsal view) with dura mater Brain with leptomeninges variably thickened by
partially removed, showing thin transparent a pale yellow exudate (ie what a predominately
leptomeninges (pia & arachnoid) overlying neutrophilic exudate looks like grossly) 
the surface. severe acute diffuse suppurative meningitis

7. Avoid using the word “lesion” in the description

 8. Morphologic Diagnosis

 Severity - mild, moderate, marked / severe

 Duration - acute, subacute, chronic

 Distribution
 8. Morphologic Diagnosis

 Severity - mild, moderate, marked / severe

 Duration - acute, subacute, chronic

 Distribution - focal, multifocal, locally-extensive, diffuse

 Nature of the lesion

- if inflammatory – type of exudate
- if degeneration – type of degeneration
- if neoplastic – type of neoplasia

 Organ (prefix) + type of disease (suffix)

- eg nephritis, nephropathy, nephrosis

+/- subcompartments - interstitial nephritis, glomerulonephritis, pyelonephritis, etc

Anatomic Terminology

 ORGAN + OPATHY (non-inflammatory; etiology unknown / unclear)

eg, Hepatopathy
Nephropathy

 ORGAN + OSIS (non-inflammatory; degeneration / necrosis)

eg, Hepatosis
Nephrosis

 ORGAN + ITIS (inflammation)

eg, Hepatitis
Nephritis
Severe

Acute

Diffuse

Fibrinonecrotic

Tracheitis
ORGAN + itis
(greek root)

+ osis
+ pathy
Necropsy Rounds
Thursdays - 4:30 PM

Postmortem Demonstration Room (1034N)

STUDENTS VISITING POSTMORTEM ROOM

- you are welcome to visit, but when you do, you must comply with the following:

❶ wear one of the labcoats hanging at the entry

❷ wear rubber boots or plastic coverings (again provided at the entry)

❸ if you are there to participate in a necropsy, coveralls must be worn

❹ wash your hands and boots thoroughly before leaving the lab