Acute Abdomen Causes
The acute abdomen is an umbrella term for sudden, severe abdominal pain requiring urgent assessment. A systematic differential covering all quadrants prevents missed diagnoses.
✦ The Mnemonic
"PAMPER Covers Acute Abdomen Causes"
Perforated ulcer · Appendicitis · Mesenteric ischaemia · Pancreatitis · Ectopic pregnancy · Ruptured AAA
Clinical Breakdown
Free air under the diaphragm on an erect CXR = visceral perforation until proven otherwise. The most common cause is perforated peptic ulcer (anterior surface); perforated sigmoid diverticular disease is the second commonest. Urgent laparotomy or laparoscopy is required after resuscitation.
The most dangerous diagnostic pitfalls in the acute abdomen: mesenteric ischaemia (pain out of proportion to signs; classical in AF/embolic cause; CT angiography is diagnostic — do not delay for bowel prep); ruptured ectopic pregnancy (always check bHCG in women of reproductive age — haemoperitoneum can present without vaginal bleeding); ruptured AAA (pulsatile mass + back/flank pain + hypotension = surgical emergency).
The 'surgical sieve' for abdominal pain by quadrant: RUQ — cholecystitis, hepatitis, right basal pneumonia; LUQ — splenic pathology, left basal pneumonia; RIF — appendicitis, Crohn's, ectopic, ovarian; LIF — diverticulitis, sigmoid volvulus, ectopic, ovarian; Central — aortic, SMA occlusion, small bowel obstruction, pancreatitis.
⭐ Clinical Pearl
Ruptured AAA has 80% out-of-hospital mortality. Any patient with the classic triad (back/flank pain, pulsatile abdominal mass, hypotension) should go directly to CT (if haemodynamically stable) or straight to the operating room (if profoundly shocked). EVAR (endovascular repair) is preferred over open repair where anatomy permits — it has lower 30-day mortality.