Abdominal pain

First rule out the dangerous causes: perforation, obstruction, bowel ischaemia, ruptured AAA, ectopic pregnancy, sepsis.

Older people and patients on steroids or opioids can look well despite serious disease.

Act now

1
Give analgesia — do not withhold it while waiting for the surgical review.
2
Nil by mouth if surgical cause possible; IV access and fluids; antiemetic; NG tube if obstructed and vomiting.

Onset, site, character, radiation; vomiting; bowels and flatus; urine output; post-op day.
Examine for peritonism, distension, hernias, pulsatile mass, catheter or palpable bladder.
Medical causes: inferior MI, DKA, lower-lobe pneumonia, pancreatitis, urinary retention, constipation.
Drug chart: opioids, anticoagulants, NSAIDs.

FBC, U&E, LFT, amylase or lipase, CRP, venous gas with lactate, glucose (ketones if diabetic), group and save.
Urine dip and pregnancy test in anyone who could be pregnant; ECG.
Erect CXR for free air; CT as advised by the senior or surgeons.

Suspected sepsis: follow the sepsis pathway.
Urinary retention: bladder scan and catheter. Constipation: laxatives, review opioids.
Pain out of proportion to examination, especially with AF: think bowel ischaemia.

Peritonism, rising lactate, suspected AAA, ischaemia, obstruction or perforation: senior and surgeons now. Positive pregnancy test with pain: gynaecology.

Paracetamol

1 g oral or IV every 6 hours (max 4 g/day; 15 mg/kg if under 50 kg).

Morphine

1–2 mg IV increments titrated to effect (opioid-naive), with an antiemetic.

Cyclizine

50 mg IV, IM or oral up to 3 times daily.

Check the BNF and your local formulary before prescribing.

Written to current guidance (NICE NG253, NG185) · sources checked 14 Nov 2026. We watch NICE for updates weekly.

Sources (3)

Reviewed by Aboodee Alhasso, MPharm MRCPharm IP on 14 Nov 2026

For healthcare professionals, as an aid to clinical judgement — not a substitute for it. Follow your local policy and ask a senior when in doubt.