23/08/2026
Causes of
Acute abdomen refers to sudden, severe abdominal symptoms that may indicate a serious intra-abdominal condition and can require urgent medical or surgical assessment.
1. Appendicitis
Obstruction of the appendix lumen, commonly by a fecalith.
Pain often begins periumbilically and later localises to the right lower quadrant/right iliac fossa.
Nausea, vomiting, anorexia and low-grade fever may occur.
Key clue: McBurney-point tenderness; guarding/rebound tenderness may occur.
2. Acute Cholecystitis
Inflammation of the gallbladder, usually caused by cystic-duct obstruction by a gallstone.
Right upper-quadrant pain, fever, nausea and vomiting.
Pain may follow a fatty meal.
Key clue: Positive Murphy's sign.
3. Acute Pancreatitis
Acute inflammation caused by premature activation of pancreatic enzymes.
Common causes include gallstones and alcohol.
Severe epigastric pain, often radiating to the back.
Nausea and vomiting are common.
Key clue: Elevated serum lipase; amylase may also rise.
4. Small Bowel Obstruction
Mechanical or functional obstruction preventing normal passage of intestinal contents.
Colicky abdominal pain, vomiting and abdominal distension.
Constipation/obstipation may occur.
Key clue: Imaging may demonstrate dilated bowel loops and air-fluid levels.
5. Gastrointestinal Perforation
Perforation of a hollow abdominal organ, e.g. perforated peptic ulcer or diverticular perforation.
Sudden, severe abdominal pain.
Guarding, rigidity and signs of peritonitis may develop.
Key clue: Free intraperitoneal air may be seen on imaging.
6. Abdominal Aortic Aneurysm (AAA)
Abnormal dilatation of the abdominal aorta.
Rupture can cause sudden severe abdominal/back pain, hypotension and shock.
A pulsatile abdominal mass may be present but is not always detectable.
Emergency: Suspected ruptured AAA requires immediate assessment and treatment.
7. Acute Mesenteric Ischemia
Reduced blood supply to the intestines.
Classically causes severe abdominal pain disproportionate to early examination findings.
Nausea, vomiting or diarrhoea may occur.
Risk factors include atrial fibrillation and atherosclerotic disease.
Key clue: Elevated lactate/metabolic acidosis can occur, especially as ischemia progresses.
Clinical Approach
History: onset, location, character, radiation, duration and associated symptoms.
Examination: ABCDE assessment, vital signs and abdominal inspection, auscultation, percussion and palpation.
Investigations: Depending on presentation—CBC/FBC, renal function, LFTs, CRP, lipase, lactate, urinalysis, pregnancy testing where appropriate, ultrasound or CT.
Management: Stabilise the patient, provide appropriate analgesia/fluids, identify the cause and obtain urgent surgical or specialist review when indicated.
🚨 Red Flags: Hemodynamic instability/shock, peritonism, rigid abdomen, GI bleeding, persistent severe pain, sepsis or rapidly deteriorating clinical condition.
⭐ Key Point: An acute abdomen is a clinical presentation, not a single diagnosis. Rapid assessment is important because some causes are life-threatening and require urgent intervention.
