Anatomical pathology Flashcards
Define epidemiology
Epidemiology is the study of disease in populations.
(who, when, where, incidence, prevalence)
Knowledge about the population characteristics of a disease is important for:
• providing aetiological clues
• planning preventive measures
• provision of adequate medical facilities
• population screening for early diagnosis.
- the incidence rate is the number of new cases of the disease occurring in a population of defined size during a defined period
- the prevalence rate is the number of cases of the disease to be found in a defined population at a stated time
[• the remission rate is the proportion of cases of the disease that recover
•the mortality rate is the number or percentage of deaths from a disease in a defined population.]
Define pathogenesis
The pathogenesis of a disease is the mechanism through which the aetiology (cause) operates to produce the pathological and clinical manifestations.
Groups of aetiological agents often cause disease by acting through the same common pathway of events.
Examples of disease pathogenesis include:
•inflammation: a response to many microorganisms and other harmful agents causing tissue injury
• degeneration: a deterioration of cells or tissues in
• response to, or failure of adaptation to, a variety of agents carcinogenesis: the mechanism by which cancer-causing
• agents result in the development of tumours
immune reactions: undesirable effects of the body’s immune system.
Define pathological and clinical manifestations
The aetiological agent (cause) acts through a pathogenetic pathway (mechanism) to produce the manifestations of disease, giving rise to clinical signs and symptoms (e.g. weight loss, shortness of breath) and the abnormal features or lesions (e.g. carcinoma of the lung) to which the clinical signs and symptoms can be attributed.
The pathological manifestations may require biochemical methods for their detection and, therefore, should not be thought of as only those visible to the unaided eye or by microscopy. The biochemical changes in the tissues and the blood are, in some instances, more important than the structural changes, many of which may appear relatively late in the course of the disease.
Structural abnormalities
Common structural abnormalities causing ill health are:
• space-occupying lesions (e.g. cysts, tumours) destroying, displacing or compressing adjacent healthy tissues
• deposition of an excessive or abnormal material in an organ (e.g. fat, amyloid)
• abnormally sited tissue (e.g. tumours, heterotopias) as
a result of invasion, metastasis or developmental abnormality
• loss of healthy tissue from a surface (e.g. ulceration) or from within a solid organ (e.g. infarction)
• obstruction to normal flow within a tube (e.g. asthma,
vascular occlusion)
• distension or rupture of a hollow structure (e.g. aneurysm, intestinal perforation).
- other structural abnormalies are only visible via microscopy
Define pathological and clinical manifestations
The aetiological agent (cause) acts through a pathogenetic pathway (mechanism) to produce the manifestations of disease, giving rise to clinical signs and symptoms (e.g. weight loss, shortness of breath) and the abnormal features or lesions (e.g. carcinoma of the lung) to which the clinical signs and symptoms can be attributed.
The pathological manifestations may require biochemical methods for their detection and, therefore, should not be thought of as only those visible to the unaided eye or by microscopy. The biochemical changes in the tissues and the blood are, in some instances, more important than the structural changes, many of which may appear relatively late in the course of the disease.
Structural abnormalities
Common structural abnormalities causing ill health are:
• space-occupying lesions (e.g. cysts, tumours) destroying, displacing or compressing adjacent healthy tissues
• deposition of an excessive or abnormal material in an organ (e.g. fat, amyloid)
• abnormally sited tissue (e.g. tumours, heterotopias) as
a result of invasion, metastasis or developmental abnormality
• loss of healthy tissue from a surface (e.g. ulceration) or from within a solid organ (e.g. infarction)
• obstruction to normal flow within a tube (e.g. asthma,
vascular occlusion)
• distension or rupture of a hollow structure (e.g. aneurysm, intestinal perforation).
- other structural abnormalities are only visible via microscopy or electron microscopy
Functional abnormalities
Examples of functional abnormalities causing ill health include:
• excessive secretion of a cell product (e.g. nasal mucus in the common cold, hormones having remote effects)
• insufficient secretion of a cell product (e.g. insulin lack in type 1 diabetes mellitus)
• impaired nerve conduction
• impaired contractility of a muscular structure.
Define complications and sequelae
Diseases may have prolonged, secondary or distant effects.
The course of a disease may be prolonged and complicated if the body’s capacity for defence, repair or regeneration is deficient.
Define prognosis (with or without disease)
The prognosis forecasts the course of the disease and, therefore, the fate of the patient.
The prognosis for any disease may be influenced by medical or surgical intervention; indeed that is the objective. So one must distinguish between the prognosis for a disease that is allowed to follow its natural course and the prognosis for the same disease in a group of patients receiving appropriate therapy.
List the categories for the causes of disease
VINDICATE
Vascular / Hemodynamic (ischaemia, haemorrhage, thrombosis, infarction, embolism)
Inflammatory
- Infective (prions, virusses, bacteria, fungi, parasites)
- Non-infective e.g. autoimmune, allergic
Neoplastic / disorders of growth
- Benign
- Malignant
Drugs / Toxins
Iatrogenic / Intervention (caused by medical examination or treatment)
Idiopathic (cause unknown)
Congenital (disease present at birth; may be genetic or not) / Genetic
Autoimmune
Trauma (physical, thermal, radiation, chemical etc.)
Endocrine / Metabolic (e.g. enzyme deficiency) / Nutritional
Heterotopia?
Patches of fundic-type gastric mucosa are occasionally found above the distal sphincter, clearly separated from the columnar-lined distal oesophagus.
These are assumed to be congenitally misplaced (heterotopic) gastric tissue which can lead to ulceration and stricturing due to local acid/ pepsin secretion.
(microscopically normal tissue in abnormal location
Heterotopia vs Metaplasia?
Heterotopia refers to congenital misplacement of tissue while metaplasia is the conversion of one type of adult tissue into a different type of adult tissue. (The end result of heterotopia and intestinal metaplasia may look the same but these processes differ fundamentally.)
Atresia
Atresia is failure of embryological canalisation resulting in complete occlusion of the lumen.
abnormal connection (fistula) between the patent proximal part of the oesophagus and the trachea = cannot swallow = aspiration bronchopneumonia
Atresia vs agenesis
Atresia = failure of embryological canalisation = complete occlusion (canal doesn’t form/disconnected)
Agenesis = failure of development of organ
Atresia vs stenosis
Atresia = complete occlusion
Stenosis = incomplete occlusion (narrowing)
Stenosis?
Narrowing of the lumen - incomplete occlusion
e.g. congenital pyloric stenosis, stenosis in colon
Diverticulum?
An outpouching of the wall of a hollow structure in the body. (specific to GIT tract)
Classification
- Congenital OR acquired
- True (contains all the layers of the normal structure from which it develops) OR false ( 1 or more layers)
- Traction (pulling) OR pulsion (pushing to increased intralumenal pressure/distention)
e.g. appendix (physiological)
Examples of specific diverticula
- Upper esophagus: Zenker’s diverticulum
- Ileum: Meckel’s diverticulum
- Sigmoid colon: Acquired diverticular disease of the colon
Complications of diverticula
- Depends on site
- Oesophageal: regurgitation, aspiration pneumonia
- Small bowel and colon: similar to appendix
What are the 3 oesophageal diverticula and describe them?
Zenker’s diverticulum:
- Upper oesophagus
- False, acquired, pulsion
Traction diverticula:
- Attached to tuberculous mediastinal lymph node
- True, acquired
Epiphrenic diverticula:
- Due to motility disorders
- Pulsion, acquired, false
What is Meckel’s diverticulum and its complications?
Meckel’s diverticulum is an outpouching of the ileum on the antimesenteric border approximately 60 to 100 cm from the ileocaecal valve caused by the incomplete regression of the vitelline (omphalomesenteric) duct.
True diverticulum
Normally asymptomatic
[May contain pancreatic or gastric mucousa]
Complications:
- peptic ulceration
- intussusception
- incarceration
- perforation
- remain patent to umbilicus - fistula
Rule of 2’s
- 2% of population
- within 2 feet of ileocecal valve
- ± 2 inches long
- often presents in children under 2
Diverticular disease of colon complications and inflammation?
Complications: (DPPFFB)
- Diverticulitis
- Peri-colic abscess
- Perforation
- Fistula
- Faecal peritonitis
- Bleeding
Inflammation:
- Scarring
- Obstruction