Topic 1: Diseases Flashcards
Appendicitis definition
- what is it
- where is it located
- blood supply
- what fills the lumen
- histology
- A blind pouch that arises from the cecum
- Most are retrocaecal (behind cecum), some are pelvic (lie in pelvic brim), less are para-ileal (next to ileum), and some have an appendix on left
- own mesentery (blood supply) called mesoappendix
- Lumen filled with mucus, faecal matter, and bacteria
- Epithelium is same as large intestine (columnar epithelium, goblet cells) and has mucosa +submucosa + muscular layer + serosa
Apendicitis: Epidemiology
- 7% of the population
- 10-30yo
- more commonly men
Appendicitis: Aetiology
Obstruction of the appendiceal lumen (50-80% cases);
- hardened faecal matter (faecolith)
- lymphoid swelling (lymphoid hyperplasia)
- obstruction of the outer wall (cecum cancer)
Appendicitis: Pathogenesis
- epithelium produced more mucus once obstructed
- increased mucus in the lumen increases pressure
- bacteria that normally live in the appendix can proliferate
- distention can cause a collapse of low-pressure blood vessels (veins)
- ischaemic mucosa due to impaired blood flow, causing cells to die and bacteria to invade
- triggers an acute inflammatory response
- vasodilation and increase vascular permeability
- proteinaceous exudate into the lumen
- further distension, ischaemia, the cycle continues without therapeutic intervention
Appendicitis: Morphology
- mucosal ulcer
- lumen fills with neutrophils, exudate and cell debris
- suppurative / purulent exudate in appendix wall, breaching epithelium and moving to the lumen
- neutrophils and oedema in muscularis layer could be from gastroenteritis
Appendicitis: Clinical manifestations
Compare signs and symptoms of early and later appendicitis.
Early:
- red, swollen and dull distal end
- dilated and congested blood vessels
- increased neutrophil count
- pain (not yet localised), colicky due to strong peristalsis contractions
- constipation
- anorexia
- nausea/ vomiting (unlikely)
- fever (cytokines TNF and IL-1 stimulate the production of prostaglandins in hypothalamus)
Next stage:
- inflammatory progression to outer surface
- fibrinosuppurative exudate
- peritonitis (rigidity on parietal peritoneum)
- constant pain shift to the right iliac fossa (not coliky)
- localised pain around appendicitis, tenderness
- abdominal muscular spasms
Appendicitis: Associated Complications
- appendiceal mass
- gangrene
- rupture
- periappendiceal abscess
- peritonitis (pus fulls peritoneal cavity)
- septicaemia (bacterial toxins go into microvascular bed)
- portal pyaemia (pus entering appendiceal vein)
- bowel obstruction (scar tissues trap bowl)
- pyaemic liver abscess (an infection spread through the portal vein)
Appendicitis: Prognosis
What makes diagnosis difficult?
- difficult is appendix is in unusual location
- females have a wide differential diagnosis
- difficult to properly examine infants
- elderly people present later
Appendicitis: What other conditions could present with acute onset pain?
- IBS
- UTI
- Pelvic inflammatory disease
- Ectopic pregnancy
Pneumonia: Definition
- what is it
- 5 classifications
- acute inflammation caused by microbial invasion of lung parenchyma
- Typical/ atypical
- Community-acquired (CAP) or nosocomial (healthcare-associated- HCAP)
- Normal host or immunocompromised
- Microbial agent
- Radiological (pathological)
Pneumonia: Pathogenesis
- Acute inflammatory response (vascular and cellular)
- Lobar pneumonia
- Bronchopneumonia
- Vasodilation: histamine, NO
- Increased permeability: histamine, prostaglandins, leukotrienes, TNFa, IL-1 - Leucocyte recruitment: adhesion, migration, chemotaxis
- Microbe recognition: opsonisation
- Removal: phagocytosis
Lobar: Congestion -> red hepatisation -> grey hepatisation -> resolution
Bronchopneumonia: patchy suppurative inflammation, multilobar, yellow-grey zones
Pneumonia: Clinicopathological correlation
Link the following clinical observations to pathological mechanisms
1. Cough
2. Consolidation on x-ray
3. Pleuritic chest pain
4. Fever, septic shock
5. Purulent exudate
6. inspiratory crackles, crepitations/ rales
7. dullness to percussion
- stimulation of sensory nerve fibres
- fibrinosupperative exudate fill alveoli
- fibrinous exudate on pleural surface
- IL-1 and TNFa released, activated by monocytes/ macrophages
- Release of bacterial N-formyl peptides
- opening of fluid-filled alveoli
- loss of resonance in consolidate alveoli
Pneumonia: Aetiology
- more likely in people with impaired defences
- extremes of age
- impaired drainage (CF, obstructive neoplasm, foreign body)
- impaired mucociliary apparatus (post-viral, smoking)
- static fluid in alveoli (pulmonary oedema)
- immunodeficiency
Pneumonia: Diagnostic investigations
- imaging
- clinical
- blood test
- cultures
- ancillary tests
Pneumonia: Community acquired
- epidemiology
- symptoms
- signs
- lab findings
- increased risk in age, winter, underlying disease
- chills, productive cough, pleuric chest pain
- fever, tachypnoea, dullness to percussion
- increased neutrophils, hypoxaemia, a causative organism found on gram stain
