Clinical cases
The acute abdomen: a case-based approach to sudden abdominal pain
This is an illustrative educational case — not a real patient — showing how a clinician approaches sudden, severe abdominal pain (the "acute abdomen"). The abdomen contains many organs, and pain in one place can come from several sources, so the assessment is a disciplined process of pattern recognition and exclusion rather than a single test. We follow a fictional presentation to show that reasoning.
Education and reference only. This article explains how treatments work in plain language — it contains no doses and is not a substitute for advice from your doctor or pharmacist. Always discuss your own treatment with a qualified clinician.
The presentation
A 24-year-old woman describes central abdominal pain that began around her belly button several hours ago and has since shifted to the lower right side, now sharp and worse with movement. She feels nauseated, has no appetite and has a mild fever. The story here is characteristic: pain that starts centrally and later localises to the right iliac fossa, with anorexia and low-grade fever, is a classic pattern — though never assumed without assessment.
The pattern of the pain tells a story
How abdominal pain behaves is diagnostically powerful. Pain that comes in waves (colicky) suggests a hollow tube contracting against an obstruction — bowel or ureteric stone. Constant, sharp pain worsened by movement suggests peritoneal irritation (inflammation of the abdominal lining), as in appendicitis. Sudden, severe "worst ever" pain raises perforation or a vascular catastrophe. Where the pain is, where it started, where it moved, and what makes it better or worse all narrow the field before any investigation.
The dangerous causes to exclude
The assessment is organised around not missing the surgical and life-threatening causes: appendicitis, a perforated organ, bowel obstruction, mesenteric ischaemia (loss of blood supply to the bowel), a ruptured or leaking abdominal aortic aneurysm, and — crucially in any woman of reproductive age — an ectopic pregnancy, which can be rapidly fatal. This is why a pregnancy test is one of the first investigations in this group, regardless of the presumed diagnosis.
Examination and tests
Examination looks for tenderness, guarding (the abdominal muscles tensing to protect an inflamed area) and signs of peritonitis. In this case there is localised tenderness and guarding in the right iliac fossa. Investigations include a pregnancy test (negative here), blood tests showing raised inflammatory markers, a urine test to help exclude a urinary cause, and imaging — ultrasound or CT — where the diagnosis is unclear. Scoring tools such as the Alvarado score can support, but not replace, clinical judgement in suspected appendicitis.
Reaching a diagnosis and what the case teaches
The migrating pain, localised peritonism, anorexia, mild fever and raised inflammatory markers together point to acute appendicitis, and the patient is referred for surgical assessment. The teaching point is the method: characterise the pain precisely, actively exclude the dangerous causes (never forgetting ectopic pregnancy and vascular emergencies), and let examination and targeted tests confirm the most likely diagnosis. An acute abdomen with signs of peritonitis or shock is a surgical emergency, and the safe default is early senior and surgical involvement.
In short
Key takeaways
- The character, site and movement of abdominal pain are highly diagnostic — colicky pain suggests obstruction, constant pain worse on movement suggests peritoneal inflammation.
- The assessment centres on excluding surgical and life-threatening causes, including appendicitis, perforation, obstruction, bowel ischaemia and aneurysm.
- A pregnancy test is essential in any woman of reproductive age — ectopic pregnancy can be rapidly fatal.
- Guarding and rebound tenderness signal peritoneal irritation and warrant urgent surgical assessment.
- Educational illustration only — sudden severe abdominal pain needs urgent medical assessment.
Answers
Frequently asked questions
Is this a real patient?
No. It is a fictional teaching case for education and is not advice for any individual.
When is abdominal pain an emergency?
Sudden severe pain, a rigid or very tender abdomen, pain with vomiting blood or collapse, or pain with pregnancy or possible pregnancy are emergencies — seek urgent care (call 999 or go to A&E).
Why is a pregnancy test done first?
In any woman of reproductive age, an ectopic pregnancy can present as abdominal pain and can be life-threatening, so it must be excluded early regardless of the suspected cause.
Go deeper
Related guides
Sources
Where this is drawn from
- NICE CKS — Acute abdominal pain
- Royal College of Surgeons — assessment of the acute abdomen
- BMJ Best Practice — Assessment of acute abdomen
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