Appendicitis Pathology

Study Notes

Obstruction of the appendiceal lumen is essential for the development of appendiceal gangrene and perforation.
Lymphoid hyperplasia narrows the lumen of the appendix, leading to luminal obstruction.
Continued mucus secretion and inflammatory exudation increase intraluminal pressure, obstructing lymphatic drainage.
Oedema and mucosal ulceration develop with bacterial translocation to the submucosa.
Resolution may occur at this point either spontaneously or in response to antibiotic therapy.

Further distension of the appendix may cause venous obstruction and ischaemia of the appendix wall.
Ischaemia leads to bacterial invasion through the muscularis propria and submucosa.
Ischaemic necrosis of the appendix wall produces gangrenous appendicitis, with free bacterial contamination of the peritoneal cavity (Peritonitis).

The greater omentum and loops of small bowel become adherent to the inflamed appendix, walling off the spread of peritoneal contamination, and resulting in a phlegmonous mass or abscess.
Rarely, appendiceal inflammation resolves, leaving a distended mucus-filled organ termed a mucocele of the appendix.

Extremes of age, immunosuppression, diabetes mellitus, and faecolith obstruction of the appendix lumen.
A free lying pelvic appendix and previous abdominal surgery that limits the ability of the greater omentum to wall off the spread of peritoneal contamination.

Two clinical syndromes of acute appendicitis: acute catarrhal (nonobstructive) & acute obstructive appendicitis.
Acute obstructive appendicitis has a more acute course, with a higher tendency for perforation.

Abdominal pain is the prime symptom, initially diffusely cramping, centered in the periumbilical region.
Pain localizes to the right lower quadrant (somatic pain) after 1-12 hours.
Cough or sudden movement exacerbates the right iliac fossa pain.
Anorexia is a constant feature, especially in children.
Nausea and one or two episodes of vomiting are common.
Constipation is the usual feature, except in preileal and postileal and pelvic appendicitis, where diarrhea occurs due to irritation.

During the first 6 hours, there is rarely any alteration in temperature or pulse rate.
After that time, slight pyrexia (37.2– 37.7°C) with a corresponding increase in the pulse rate to 80 or 90 is usual.
Temperature elevation is rarely more than 1°C.
Changes of greater magnitude usually indicate that a complication has occurred or that another diagnosis should be considered.
The patient is asked to point to where the pain began and where it moved (the pointing sign).
Cough tenderness is an important physical sign that differentiates acute appendicitis from right-sided ureteric colic.
Localized abdominal tenderness is often maximal at or near the McBurney’s point.
Direct rebound tenderness is usually present (Blumberg sign).
Rovsing’s sign (referred or indirect rebound tenderness) may be present.
Psoas test: pain on hyperextension of the patient’s right thigh indicates that the inflamed appendix is in close proximity to the psoas muscle.