Acute appendicitis is the most common acute abdominal condition requiring surgery. It can occur at any age but is most common in young people aged 10-20 years.

Pathogenesis

• lymphoid hyperplasia or a faecolith → obstruction of appendiceal lumen → gut organisms invading the appendix wall → oedema, ischaemia +/- perforation

Abdominal pain is seen in the vast majority of patients:

• peri-umbilical abdominal pain (visceral stretching of appendix lumen and appendix is midgut structure) radiating to the right iliac fossa (RIF) due to localised parietal peritoneal inflammation.
• the migration of the pain from the centre to the RIF has been shown to be one of the strongest indicators of appendicitis
• patients often report the pain being worse on coughing or going over speed bumps. Children typically can't hop on the right leg due to the pain.

Other features:

• vomit once or twice but marked and persistent vomiting is unusual

• diarrhoea is rare. However, pelvic appendicitis may cause localised rectal irritation of some loose stools. A pelvic abscess may also cause diarrhoea

• mild pyrexia is common - temperature is usually 37.5-38C. Higher temperatures are more typical of conditions like mesenteric adenitis

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• anorexia is very common. It is very unusual for patients with appendicitis to be hungry

• around 50% of patients have the typical symptoms of anorexia, peri-umbilical pain and nausea followed by more localised right lower quadrant pain

Examination

• generalised peritonitis if perforation has occurred or localised peritonism
  • rebound and percussion tenderness, guarding and rigidity
• retrocaecal appendicitis may have relatively few signs
• digital rectal examination may reveal boggy sensation if pelvic abscess is present, or even right-sided tenderness with a pelvic appendix
• classical signs
  • Rovsing's sign (palpation in the LIF causes pain in the RIF) is now thought to be of limited value
  • psoas sign: pain on extending hip if retrocaecal appendix

Diagnosis

• typically raised inflammatory markers coupled with compatible history and examination findings should be enough to justify appendicectomy