Acute Appendicitis
Luminal obstruction of the appendix triggers a closed-loop build-up of pressure that progresses predictably from visceral pain to localised peritonism, ischaemia and, if untreated, perforation.
In a nutshell
Luminal obstruction of the appendix raises intraluminal pressure in a closed loop, causing visceral peri-umbilical pain that migrates to sharp right iliac fossa pain as inflammation reaches the parietal peritoneum. Untreated, the wall becomes ischaemic and perforates, so definitive treatment is timely appendicectomy.
Classic presentation
A young patient with peri-umbilical pain migrating over hours to constant right iliac fossa pain, anorexia, low-grade fever and tenderness with guarding at McBurney's point.
Key points
- The migratory pattern of pain (vague peri-umbilical to sharp right iliac fossa) reflects the shift from visceral (T10) to somatic (parietal peritoneal) innervation, and is the most discriminating feature in the history.
- Anorexia is a near-universal early feature; its absence should prompt reconsideration of the diagnosis.
- Appendicitis remains a clinical diagnosis; imaging (ultrasound or CT) supports rather than replaces clinical judgement, especially in atypical or equivocal presentations.
- Perforation risk rises the longer luminal pressure goes unrelieved, which is why suspected appendicitis is managed urgently rather than electively.
- An appendix mass or abscess may be managed initially with antibiotics rather than immediate surgery, unlike straightforward acute appendicitis.
First-line investigation
Clinical assessment supported by FBC/CRP and, where the diagnosis is unclear, CT (or ultrasound in children and pregnancy) to demonstrate the obstructed, inflamed appendix.
First-line management
Resuscitation, analgesia and antiemetics, empirical antibiotics if indicated, followed by urgent laparoscopic appendicectomy.
Exam traps
- Sudden relief of pain in a patient with appendicitis can mean perforation, not improvement; the peritonitis that follows is often worse than the original pain.
- A normal white cell count and CRP do not exclude early appendicitis; the diagnosis is clinical.
- In pregnancy the appendix is displaced upward and laterally by the gravid uterus, so pain may be felt higher than the classic right iliac fossa position.
- Analgesia should be given early and does not mask peritonism on examination; withholding it is outdated practice.
Educational content pending clinical review. Not medical advice.