A 25-year-old man presents with central abdominal pain that shifted to the right iliac fossa over a few hours, with anorexia and nausea. He is tender at McBurney's point with guarding. What is the most likely diagnosis?

Answer: B. Acute appendicitis

Acute appendicitis

The classic history - periumbilical (central) colicky pain that shifts to the right iliac fossa (RIF), with anorexia, nausea and tenderness at McBurney's point with guarding - is diagnostic of acute appendicitis, the commonest cause of an acute abdomen.

Why the pain shifts

• Early visceral (midgut) pain is felt centrally/periumbilically.
• As inflammation involves the parietal peritoneum over the appendix, somatic pain localises to the RIF (McBurney's point), aggravated by movement and coughing.

Supporting features

• Anorexia - a useful and constant feature.
• Low-grade fever, coated tongue, RIF tenderness, guarding, rebound/percussion tenderness, Rovsing's sign.

Epidemiology

Common in childhood and early adult life, peaking in the teens to early 20s; rare in infancy.