Page created on April 11, 2022. Not updated since.
For “differential diagnosis of abdominal pain”, see topic 64.
Introduction and epidemiology
Acute appendicitis refers to acute inflammation of the vermiform appendix and is a common cause of acute abdomen. Rapid management is important to prevent complications such as perforation of the appendix.
The lifetime incidence of appendicitis is 9% for men and 7% for women. The peak incidence is in the second and third decades of life, but it may occur at any age. The incidence of acute appendicitis has been decreasing since the 1970s, for reasons not known.
For etiology and pathomechanism, see the corresponding pathology 2 topic. For treatment, see the corresponding surgery topic.
The classical clinical features of acute appendicitis are:
- Initial diffuse periumbilical pain which evolves into peritonitic pain in the right lower quadrant
- Anorexia (decreased appetite)
- Nausea and vomiting
Other possible symptoms include fever and abnormal bowel habits.
Various physical signs may be positive in acute appendicitis, including McBurney point tenderness, Rovsing sign, psoas sign, and obturator sign (topic A25 in surgery). Because of the localised peritonitis over the appendix, peritonitis signs like guarding, rebound tenderness, and heel-drop test may be positive and elicit pain in the right lower quadrant.
Diffuse peritonitis may be a sign of perforated appendicitis.
There is considerable anatomical variation in the location of the free end of the appendix, which will influence the site of pain and findings on physical examination. A retrocaecal appendix may not cause localised tenderness in the right lower quadrant (because localised peritonitis does not occur). A pelvic appendix may cause localised tenderness well below McBurney’s point.
- Catarrhal appendicitis
- Non-destructive inflammation, appendix is erythematous and swollen
- Suppurative appendicitis
- Bacterial inflammation, ulceration occurs
- Phlegmonous appendicitis
- Destructive, appendix is filled with purulent fluid
- Gangrenous appendicitis
- Necrotic appendix, with black necrotic areas
- Perforated appendicitis
- Perforation -> localised pericoecal abscess or diffuse peritonitis
“Complicated” appendicitis refers to the presence of periappendicular infiltration, periappendicular abscess, perforation, or peritonitis.
Diagnosis and evaluation
A normal WBC count is unlikely in the case of acute appendicitis, as leukocytosis is present in > 80% of cases. The higher the WBC count, the higher the chance for gangrenous or perforated appendicitis. CRP is also frequently elevated.
In some countries (like Norway), imaging is usually not performed if the clinical presentation is very suspicious for acute appendicitis. If imaging is to be performed, low-dose abdominal CT with contrast or abdominal ultrasound are the modalities of choice. These may reveal suspicious features such as thickening and enhancement of the appendiceal wall. Imaging will also reveal features of perforation if present.
Only histology can confirm the diagnosis of appendicitis.