Red flags
- Peritonism (guarding, rigidity, rebound, involuntary splinting) - suggests perforation/peritonitis, surgical emergency
- Haemodynamic instability with abdominal pain - ruptured AAA, ectopic pregnancy, GI haemorrhage until excluded
- Pain out of proportion to examination findings - classic for mesenteric ischaemia, easily missed early
- Sudden-onset tearing pain radiating to the back, especially with pulsatile mass or known AAA - ruptured/leaking aneurysm
- Pain + fever + jaundice - ascending cholangitis (Charcot's triad) - needs urgent biliary decompression
- Any woman of reproductive age with abdominal pain - exclude ectopic pregnancy (beta-hCG) before other work-up
Differential by mechanism
By pain character
- Visceral (dull, poorly localised, midline) - early appendicitis, bowel obstruction, biliary colic
- Parietal/somatic (sharp, well-localised, worse with movement) - once inflammation reaches the parietal peritoneum (e.g. appendicitis localising to RIF)
- Referred - diaphragmatic irritation to shoulder tip (splenic/hepatic/subphrenic pathology), renal colic to groin
By region and mechanism
| Region | Common | Don't miss |
|---|---|---|
| RUQ | Biliary colic, cholecystitis, hepatitis | Cholangitis, liver abscess |
| Epigastric | PUD, GORD, pancreatitis | MI (always consider), AAA |
| RIF | Appendicitis, mesenteric adenitis | Ectopic, ovarian torsion, Crohn's |
- LIF: diverticulitis common; ovarian torsion/ectopic don't miss
- Generalised: gastroenteritis, obstruction, mesenteric ischaemia, DKA, perforation (any site)
Extra-abdominal mimics
- Inferior MI, DKA, lower lobe pneumonia, testicular torsion, herpes zoster (pre-eruptive)
Focused history
- SOCRATES - onset (sudden vs gradual), character, radiation, associated symptoms, timing, exacerbating/relieving factors
- Relationship to food (biliary colic post-fatty meal, PUD pattern), bowel habit change, last menstrual period/sexual history if relevant
- Vomiting before pain (surgical abdomen less likely) vs pain before vomiting (more concerning for surgical cause)
- Medication review - NSAIDs, anticoagulants, corticosteroids, opioids (masking signs, constipation)
- Past surgical history (adhesions), alcohol history (pancreatitis)
Focused examination
- Vital signs first - tachycardia/hypotension/fever change the whole approach
- Inspection (distension, scars, visible peristalsis), palpation (tenderness, guarding, rebound, masses), percussion (peritonism, shifting dullness), auscultation (bowel sounds - absent in ileus/late obstruction, tinkling in obstruction)
- Specific signs: Murphy's sign (cholecystitis), McBurney's point/Rovsing's sign (appendicitis), Psoas/obturator sign
- Digital rectal exam and pelvic/genital exam where relevant to the differential - often omitted, frequently diagnostic
Investigation strategy
- Bedside: urinalysis (renal colic, UTI), beta-hCG (any woman of reproductive age), ECG (inferior MI mimicking epigastric pain)
- Bloods: FBE, UEC, LFT, lipase/amylase, CRP, group and hold/crossmatch if bleeding or surgery likely, VBG/lactate if unwell (raised lactate - concern for ischaemia)
- Imaging: erect CXR (free air under diaphragm - perforation), CT abdomen/pelvis with contrast - the workhorse for undifferentiated significant pain; ultrasound first-line for biliary/gynaecological/renal pathology; avoid unnecessary radiation in young women (consider USG/MRI first)
- Match imaging urgency to clinical instability - do not delay resuscitation/surgical review awaiting imaging in a peritonitic or unstable patient
Management
Stabilise first, diagnose in parallel
- IV access, analgesia (do not withhold opioids pending surgical review - does not obscure diagnosis and is a historical myth), antiemetics, fluid resuscitation if unwell
- Early surgical review for any peritonism, haemodynamic instability, or high suspicion of a surgical abdomen - do not wait for full work-up to complete
- NBM if surgery/procedure likely
Once a working diagnosis is reached
- Direct management to the specific cause (see individual disease notes - biliary disease, pancreatitis, PUD, diverticulitis, obstruction, etc.)
- Serial reassessment - abdominal examination findings evolve; a normal initial exam does not exclude an evolving surgical process
Traps
- Withholding analgesia "until surgery has seen the patient" - outdated practice, adequate analgesia does not mask peritonism
- Forgetting beta-hCG in a woman of reproductive age with abdominal pain - ectopic pregnancy is rapidly fatal if missed
- Attributing epigastric pain to "reflux" without an ECG in a patient with cardiac risk factors
- Discharging a patient with a normal single examination when the pain is early/evolving (e.g. early appendicitis before localisation) - safety-net and arrange review
- Missing mesenteric ischaemia because examination findings are reassuring relative to the severity of pain reported
Talk track
1. Vitals and pregnancy test before anything else
- "Before I build a differential, I check if this patient is haemodynamically stable and, if relevant, pregnant - those two facts change the whole pathway."
2. Pain out of proportion is a diagnosis to actively exclude
- "If the pain looks worse than the abdomen feels, I'm thinking ischaemia until I've got a reason not to."
8 of 8 sections written · drafted 2026-09-14