Path Notes: Appendix and Acute APpendicitis *******:)

Question 1

Describe the normal gross anatomy of the appendix

Answer 1

1. In adults, normally 6-7cm long
2. Partially anchored by mesentery from adjacent ileum
3. Extremely rich in lymphoid tissue of the mucosa and submucosa
4. This lymphoid tissue undergoes progressive atrophy throughout life
5. Distal portion can undergo fibrous obliteration

Question 2

What is acute appendicitis?

Answer 2

Acute inflammation of the appendix

Question 3

Describe the pathogenesis of acute appendicitis

Answer 3

*50-80% of appendicitis cases are caused by luminal obstruction at the base of the appendix. The significant minority are not associated with obstruction.

1. Lumen becomes obstructed by:
   - Faeces (Faecilith) - most common
   - Foreign body
   - Parasites (less common)
   - Tumour (less common)
   - Gall stones (less common)
2. Bacteria proliferate within the rest of the lumen, attracting neutrophils
3. Neutrophillic infiltrate results in purulent materials, which leads to:
   - Oedema (immune response)
   - Increased luminal pressure (from pus filling lumen)
4. This leads to bacterial invasion of the wall
5. At this point, stretch receptors have been activated, and central abdo pain is felt
6. With increasing pressures, venous and eventually arterial blood supply is pccluded, leading to ischaemic necrosis
7. At this point, RIF pain is felt, largely due to irritation of surrounding, somatically innervated, structures
8. As the disease progresses, there is increased necrosis and subsequently decreased wall strength. This leads to an increased risk of rupture

Question 4

Describe the macroscopic appearance of appendicitis

Answer 4

Generally, the appendix will have a:

• Dull, granular, red serosal membrane appearance with adherent fibrin
• If necrosis severe, may have green/black appearance, indicative of acute gangrenous appendicitis

Question 5

Describe the microscopic features of appendicitis

Answer 5

There is a progression of microscopic features.

At the baseline, there is scant neutrophillic infiltrate, until…

1. Early Acute Appendicitis:
   - Neutrophillic infiltration of the muscularis
   - Gradually worsening inflammation, ulceration, foci of suppurative necrosis in the mucosa
   - Focal abscesses may form in the wall
2. Acute Suppurative Appendicitis:
   - Involves further compromise
   - Large areas of haemorrhagic ulceration
   - Gangrenous necrosis that extends to the serosa
3. Acute Gangrenous Appendicitis
4. Potential complication: Rupture, leading to:
   - Suppurative Peritonitis
   - Abscess formation
   - Sepsis

Question 6

Describe the epidemiology of Appendicitis:

Answer 6

Overall, there is ~7% lifetime risk of appendicitis.

Tends to be a disease of adolescents and young adults

Affects slightly more men than women

Question 7

Describe the progression of events in terms of clinical presentation of an individual experiencing appendicitis

Answer 7

1. Central abdo pain
2. Then more localised RIF pain
3. Nausea and vomiting
4. Abdominal tenderness - McBurney’s sign positive
5. Mild fever
6. Increased WCC

*Varied positions of appendixes may lead to different pain locations

Question 8

What is the major complication associated with appendicitis, and what is the associated risk of mortality?

Answer 8

Perforation or abscess formation

2% mortality risk with rupture

Question 9

What are the major differential diagnoses to exclude when diagnosing appendicitis?

Answer 9

Mesenteric lymphadenitis (usually secondary to yersinia or a virus)

Systemic Viral Infection

Acute Salpingitis

Ectopic Pregnancy***

Cystic Fibrosis

Mittelchmerz

Meckel Diverticulitis