patho - appendicitis

Question 1

what is acute appendicitis?

Answer 1

acute- rapid onset
appendicitis- inflammation of the appendix

Question 2

what are the possible causes of inflammation?

Answer 2

• infection (& toxins)
• tissue necrosis (ischaemia, trauma, chemical injury)
• foreign bodies
• immune reactions (autoimmunity, hypersensitivity)

Question 3

what is acute inflammation?

Answer 3

rapid and short-term immune response to injury, infection, or irritations, etc.

Question 4

what are the 5 cardinal signs of acute inflammation?

Answer 4

1. warmth
2. redness
3. swelling
4. pain
5. loss of function

systemic symptom: fever

Question 5

what are the cells involved in acute inflammation?

Answer 5

mast cells, macrophages, neutrophils, leukocytes

Question 6

what are the mediators involved in causing warmth in acute inflammation?

Answer 6

warmth: caused by vasodilation, due to action of prostaglandin and histamine

Question 7

what are the mediators involved in causing redness in acute inflammation?

Answer 7

redness: caused by vasodilation, due to action of prostaglandin and histamine

Question 8

what are the mediators involved in causing swelling in acute inflammation?

Answer 8

swelling: caused by increased vascular permeability causing exudation, due to histamines, leukotrienes, cytokines C3a, C5a and serotonin

Question 9

what are the mediators involved in causing pain in acute inflammation?

Answer 9

pain: caused by stimulation of nerve endings, due to bradykinin and prostaglandin

Question 10

what are the mediators involved in causing fever in acute inflammation? what immune cells are involved?

Answer 10

cytokines TNF-alpha, IL-1
also: prostaglandin

produced by activated macrophages in response to PAMPs (pathogen-associated molecular patterns) due to infections

Question 11

what is the difference between exudation and transudation?

Answer 11

exudation:
- caused by leakage of fluid from surrounding tissues due to damage or inflammation out
- the fluid has high protein content

transudation:
- due to elevated hydrostatic blood pressure and low oncotic blood pressure, causing movement of fluid from the blood vessels out
- the fluid is of lower protein content.

Question 12

what are the outcomes of acute inflammation?

Answer 12

• resolution
• fibrosis
• chronic inflammation

Question 13

what are the similarities and differences between acute and chronic inflammation?

Answer 13

• both are exudative
• acute is fast-onset, chronic is slow-onset
• acute involves neutrophil accumulation, chronic involves macrophage and lymphocyte accumulation
• acute involves mild and self-limited tissue damage and fibrosis, chronic involves more severe and progressive tissue damage and fibrosis

Question 14

what are the typical symptoms and/or clinical signs that patients with acute appendicitis present with?

Answer 14

• pain in the right iliac fossa
• fever

Question 15

what is the pathogenesis of acute appendicitis?

Answer 15

1. obstruction of lumen (can be due to: fecolith, foreign matter, or lymphoid hyperplasia)
2. results in multiplication of luminal bacteria
3. which eventually invades mucosa and wall
4. causing acute inflammation
5. necrosis and ulceration

Question 16

what are some possible causes of acute appendicitis?

Answer 16

main concept - OBSTRUCTION of appendix lumen

can be caused by:
- fecolith (hard poop)
- foreign matter
- lymphoid hyperplasia
- tumour

Question 17

what are some gross features of acute appendicitis?

Answer 17

• enlarged/ swollen and congested
• thick, yellowish fibrinopurulent exudate covering the appendix serosa
• mucosal ulceration (if specimen is cut to expose mucosa)
• lumen contains pus
• dark areas of haemorrhage
• (less likely): pale areas of necrosis

Question 18

what conditions other than acute appendicitis may present with pain in the right iliac fossa?

Answer 18

• colonic causes: colon cancer, diverticulitis, Meckel’s diverticulum, intussusception
• female repro: ovarian cysts, ovarian torsion, ectopic pregnancy
• urological: UTI, kidney stones

Question 19

what are some histological features of cute appendicitis?

Answer 19

main ones:
- necrotic debris
- haemorrhage, congestion
- oedema, turgidity
- causative pathogens
- fibrinopurulent exudate (especially in lumen, serosa)
- transmural infiltration by neutrophils
- mucosal ulceration

others:
- loss of normal crypts, MALT, and glandular elements in mucosa of normal appendix -> replaced by neutrophils, shows mucosal ulceration
- many many neutrophils, especially in the muscularis propria layer
- neutrophils found across the full thickness of the wall of appendix (therefore: transmural inflammation)
- opaque serosa (due to fibrinopurulent exudate, normally translucent)

Question 20

what are some complications of untreated appendicitis? how does each complication arise?

Answer 20

• generalised peritonitis
• pelvic abscess
• subphrenic abscess

all of these arise due to: perforation (ie. rupture or breach of appendix wall) of the inflammed appendix -> leading to release of contents (bacteria and faecal content)

released into abdo -> widespread inflammation of peritoneum
infx spread to pelvic region -> pelvic abcesses
infx spread to into upper abdo -> subphrenic abscess (abscess beneath the diaphragm)

Question 21

what are the components of pus?

Answer 21

• many neutrophils
• cell debris
• causative microbe

Question 22

what kind of pathogens tend to result in purulent exudation?

Answer 22

pyogenic bacteria