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
Diverticulum vs aneurysm
diverticulum = bulge in intestinal tract
aneurysm = an abnormal outward bulge in the cardiovascular system (heart or blood vessels)
Where is the diverticulum disease most common?
Sigmoid colon
Hernia and explain 2 “common” ones?
Bulge / protrusion of organ through the structure or muscle that usually contains it
Examples: hiatus hernia, congenital diaphragmatic hernia, inguinal, femoral, umbilical, incisional hernia
Hiatus hernia is defined as the protrusion of the upper part of the stomach into the thorax via the diaphragmatic orifice.
Congenital diaphragmatic hernia;
Congenital defect in diaphragm through which stomach, intestine, spleen & liver may herniate into left thoracic cavity. May cause pulmonary hypoplasia & respiratory failure.
Diverticulum vs hernia?
Diverticulum = outpouching/bulge of the wall of hollow structures in the GI tract
Hernia = bulge of an organ through the structure/muscle that contains it
Achalasia?
- Loss of contractility in the oesophagus
- Failure of the relaxation of the LES (lower oesophageal sphincter)
- Results in slowing or retention of food bolus with increasing obstruction and dilatation of oesophagus above LES
- Presents with progressive dysphagia and vomiting of undigested food
Complications of achalasia?
- Squamous cell carcinoma
- Infections: candida oesophagitits
- Lower oesophagus diverticula
- Aspiration with pneumonia or airway obstruction
List other disorders of oesophageal motility
- Systemic sclerosis : atrophy and fibrosis of smooth muscle
- Chaga’s disease: degeneration of intrinsic nerves (South American trypanosomiasis)
[cause unco-ordinated muscle activity in the oesophagus]
Difference between primary and secondary achalasia?
Primary - benign disorder of oesophageal motility
Secondary - mostly caused by malignancy
Give an example of a secondary cause of achalasia
Chaga’s disease
Does Congenital pyloric stenosis typically presents clinically with constipation or diarrhoea?
No
What is Hirschsprung’s disease?
- Failure of migration of neuroblast from vagus to developing gut
- Results in intramural parasympathetic nerve plexus failing to develop
- parasympathetic tone (contractions) = modulated by ganglia by sympathetic innervation
- absence of myenteric ganglia = intact extramural parasympathetic supply unchecked by sympathetic modulation = spasms of circular muscle = obstruction
- Results in a narrowed distal segment which leads to proximal colonic dilatation and failure of colonic motility in neonatal period
- Presents with constipation
Histology:
- absence of ganglion cells in submucousa and myenteric plexus
- proliferation of cholinergic nerves in narrowed segment
Oesophageal varices?
- localised dilatations of veins
- blood flow through liver impaired = increased pressure within portal vein = blood forced into small veins (mucousa of oesophagus) = porto systemic shunt
- portal hypertension = veins in oesophageal mucousa congested and dilated = veins elevate the mucousa and protrude into oesophageal lumen = easily traumatised by food passing and will bleed (acute haemorrhage)
Mallory-Weiss tears?
- Rupture of oesophageal mucousa
- May cause upper GIT bleed
- Bleeding can stop spontaneously
Similarities between Mallory- Weiss tear and Boerhaave syndrome?
- Occur at gastro-esophageal junction
- Related to repeated retching, forceful vomiting or trauma.
Boerhaave syndrome
- Perforation of the full thickness of the oesophageal wall
- Usually on left posterolateral aspect of distal oesophagus
- Requires surgical repair
- High morbidity and mortality
Anorectal anomalies
- Malformations affecting termination of large bowel
Categorized: high, intermediate or low – relative to the puborectalis sling of levator ani.
- Low lesions: stenotic anus / ectopic anus.
- High lesions: anal & anorectal agenesis ± fistula.
Associated fistula: into bowel, perineum, vagina, urethra, bladder.
Associated congenital abnormalities more common with high lesions.: GU, heart or skeletal lesions.
Approximately ⅓ have serious urological abnormalites
• a primitive cloacae = where the alimentary, urinary and
genital tracts open into a single orifice
• anorectal agenesis and rectal atresia = where the rectum ends superior to the puborectalis muscle and the anal canal and the rectum are not connected
• an ectopic or imperforate anus = where the anus is in the normal position but a thin layer of tissue separates the anal canal from the exterior.
List and describe the 4 types of mechanical obstructions
- herniation = when a segment of bowel becomes trapped in a defect in either the posterior peritoneum or mesentery (internal herniation), or herniates into an inguinal or paraumbilical peritoneal sac.
- adhesion = caused by intra-abdominal inflammatory process (appendicitis or endometriosis) or previous surgery
- intussusception = An intussusception is an invagination of one segment of bowel into another, resulting in intestinal obstruction. [usually a lesion in the wall that disturbs peristalsis and results in this shift]
- volvulus = twist in the bowel that occludes lumen. Volvulus occurs around a ‘fulcrum’ such as a Meckel’s diverticulum or a congenital band of fibrous tissue, or around an abnormally long mesentery or long sigmoid colon.
Is Hirschsprung’s disease achalasia of the rectum?
yes
Which part is an increased number of ganglion cells found?
dilated (not constricted part)
Is Hirschsprung disease a common cause of constipation in adults?
no (not in adults but neonates)
Describe the relative importance of history versus physical examination in the evaluation of gastro-intestinal problems.
History = symptoms: complaints coming from the patient
- Very important in patients that have significant non-acute gastrointestinal pathology as they do not exhibit abnormal physical signs (cancer)
Physical examination = signs: changes observed by clinician
Describe elective abdominal situations
- can follow the orderly sequence of history, examination, further special investigation (if deemed necessary) and referral/treatment.
- clinical signs absent
- absence of sign does not = absence of serious pathology
- functional = polysymptomatic and can be due to stress
- serious pathology = localised pain
- non-specific symptoms may be found in patients with poor nutrition as a result of foregut disease
Sometime there is an overlap of symptoms:
- Patients with upper GI problems my complain of “constipation” because of inadequate fluid and fibre intake.
- Patients with early colon carcinoma may present with dyspepsia and/or heartburn.
Describe acute abdominal situations
- normal sequence not appropriate
- resuscitation may be needed before history
- proper pain relief facilitates clinical evaluation
Signs:
- involuntary guarding = something beneath the area being palpated is “sore”
- rigidity = underlying parietal peritoneum is inflamed. sometimes becomes temporarily less pronounced 8 hours after perforation
- percussion tenderness = more reliable sign of inflammation of underlying parietal peritoneum (better than rebound tenderness)
Difference between visceral and somatic pain?
Visceral
- autonomic nerves
- caused by distension, stretching, inflammation or oxygen deficit in hollow muscular structures
- poorly localised
- perceived over a number of spinal levels, since afferent automatic nerves connect to several spinal nerves (e.g radiation)
- radiation = spreading of pain some distance from origin of site
- not relieved by lying still
Somatic pain
- transmitted from outset by somatic nerves
- originates from structures supplied by this nerve
- better localised and sharper
- pain can be referred to distant parts (i.e pain from shoulder tip the parietal peritoneum lining the undersurface of the diaphragm)
- made worse by movement
List other important questions to ask with regards to abdominal pain
- precipitating factors
- relieving factors
- associated symptoms
- acute pain = suggests mechanical even if onset is sudden
- chronic = inflammation or infection
How do you approach anorexia, nausea and vomiting, altered bowel movement and jaundice
Anorexia
- don’t have and appetite and scared to eat due to pain that occurs
Nausea and vomiting
- nausea = feeling of wanting to vomit but don’t necessarily vomit (nauseated)
- not always GIT related
- find out the quality and content on the vomitus
- is it associated with pain? did the pain come before or after? before = surgery, after = infection
Altered bowel movement
- do they really have diahhroea or constipation
- diameter of stool?
- sense of incomplete evacuation
GI blood loss
- make sure its actually hematamesis and not spat out, coughed out or from nose
- melaena = chemical change in haemoglobin pigment = upper GIT bleed
- blood in stool doesn’t tell you where in the GI tract its from
- blood loss is microscopic = faecal blood occult test
- iron preparations cause black stool
- breast-fed baby vomiting blood = check moms breast
Jaundice
- pruritis and/or pale stool = obstructive jaundice
- jaundice with fever, rigors and abdominal pain = bacteria cholangitis = surgery
- hepatitis = bright yellow
- obstructive = darker yellow
Steps in examining the abdomen?
Inspection
- organic or functional pain
- abdominal distention
- hernias in groin area
Palpation
- gentle
- early movement of upper abdominal mass = solid tissue between mass and diaphragm
- late = compressible tissue
- is mass pulsatile?
Percussion
- abnormal dullness or resonance
