The Acute Abdomen
Sudden abdominal pain reflects one of two mechanisms: a hollow viscus obstructing and distending (colic) or the peritoneum being inflamed and irritated (peritonism), and telling them apart, not naming a diagnosis, decides whether a patient needs the theatre now.
In a nutshell
Acute abdominal pain is triaged first by mechanism, not diagnosis: colic (a hollow tube contracting against an obstruction, waxing and waning, patient restless) versus peritonism (inflamed parietal peritoneum, constant and localised, patient still). Peritonism and instability drive urgent surgical escalation.
Classic presentation
A patient with sudden abdominal pain who either writhes with waxing-and-waning colicky pain, or lies still, unwilling to move, with constant localised pain, tenderness and guarding on examination.
Key points
- Colic reflects a hollow viscus obstructing (bowel, ureter, biliary tree); peritonism reflects inflammation reaching the somatically innervated parietal peritoneum; the two have opposite behaviour patterns.
- A surgical sieve applied by abdominal region (right upper quadrant, epigastric, iliac fossae, generalised) rapidly narrows the differential before any test result is back.
- Resuscitation and analgesia take priority over establishing an exact diagnosis in an unstable or peritonitic patient.
- Generalised peritonitis, haemodynamic instability, pain out of proportion to findings, or free air on imaging are all indications for urgent senior surgical review.
- Simple bedside tests (urinalysis, pregnancy test, glucose) can redirect the entire differential within minutes.
First-line investigation
Bedside assessment (vital signs, urinalysis, pregnancy test) and bloods in parallel with resuscitation, followed by CT once the patient is stable enough.
First-line management
ABCDE resuscitation with analgesia, then targeted investigation; escalate immediately to emergency surgery if there is generalised peritonitis, perforation or instability.
Exam traps
- Pain out of proportion to examination findings is the classic clue to mesenteric ischaemia: do not be reassured by a soft abdomen.
- A colicky pattern that becomes constant suggests a complication (e.g. strangulation, perforation) and should prompt urgent reassessment, not reassurance.
- Do not wait for a CT to treat an unstable, peritonitic patient; resuscitate and involve surgeons immediately.
- Always check a pregnancy test and urinalysis early; ectopic pregnancy and urinary tract pathology are common, easily missed mimics of a surgical abdomen.
Educational content pending clinical review. Not medical advice.