Reasoning GP · Algorithm · 1-page summary
Abdominal pain in adults
For: adults ≥18, acute to chronic pain; GP or OOH/111, face to face or remote. Not for: children (children's algorithm) or known pregnancy (own pathway; the ectopic screen still applies).
Core rule: before the history ask — is the abdomen surgical, is the patient shocked, could she be pregnant? Pain out of proportion to the examination, with a pulsatile mass or with hypotension is a vascular emergency. The old, frail and immunosuppressed present late and softly.
0Stop — call 999 now — before any history
- Shock on the whole picture (perfusion, mental state, pulse, BP, trajectory; no single cut-off) · peritonism with compromise · haematemesis or melaena with instability · fever with jaundice and rigors · tender irreducible groin or scrotal lump → 999
- Vascular: sudden severe pain with a pulsatile mass, or back/flank pain with collapse over 50 (“suspected ruptured AAA”); severe constant pain, soft abdomen, AF or vascular disease (“query mesenteric ischaemia”) → 999
- Positive pregnancy test with pain plus instability, syncope, significant bleeding or shoulder-tip pain → 999
- While waiting: ABCDE, observations, nil by mouth, onset time. Analgesia is permitted. Do not delay transfer for bloods, urine or imaging; do not palpate a suspected AAA repeatedly; no laxative, enema or PPI and review.
1Triage — onset and pattern
| Onset | Think → action |
|---|---|
| Instant, maximal | Perforation, AAA, ectopic, torsion → blocks 0–2 now |
| Hours, migrating | Appendicitis → Same-day surgical |
| Colicky waves | Obstruction, renal or biliary colic — obstruction first |
| Days–weeks | Inflammatory, malignant → NG12 row, block 2 |
2Screen — one row is enough
- Could be pregnant (even on contraception) → test; positive + stable → EPU today. Sudden unilateral pain + vomiting (ovarian torsion) → Same-day gynaecology, even if eased.
- Testicular torsion → Immediate emergency urology/surgery (4–6 h window).
- Peritonism, epigastric pain to back with vomiting, pain on NSAIDs or steroids; obstruction (vomiting, distension, no flatus; check both groins) → Same-day surgical, 999 if unstable.
- Sepsis or cholangitis (fever + RUQ pain + jaundice); loin pain, fever, vomiting → Same-day acute; 999 if septic or jaundice with rigors.
- Upper GI bleed (haematemesis, coffee-ground vomit, melaena) → Same-day acute; 999 if haematemesis or shock.
- NG12 → Suspected cancer pathway: mass or ascites · 40+ weight loss → FIT (≥10 µg Hb/g → refer) · 60+ weight loss + new diabetes or bowel change → CT · 55+ weight loss + upper pain, or dysphagia · jaundice 40+ · women 40+ persistent bloating → CA-125 + urgent ultrasound, never CA-125 alone.
3Assess — once blocks 0–2 are answered
☐ Pulse, BP + postural drop, RR, SpO₂, temp, GCS ☐ Ketones if diabetic, on SGLT2 inhibitor or vomiting ☐ ECG if epigastric pain over 40 ☐ Groins and scrotum, always; PR/pelvic only if indicated, chaperone
Not in the abdomen: DKA (euglycaemic on SGLT2i — withhold), inferior MI, pneumonia, PE, retention. Not: CA 19-9, bowel sounds, a dipstick alone with pelvic pain or over 65.
4Classify — only if the screen is negative
- Appendicitis — pain migrating to RIF over 6–24 h, anorexia → Same-day surgical; normal bloods do not exclude it. Diverticulitis — LIF, fever, over 50 → block 5.
- Biliary colic — post-prandial 1–6 h, no fever → ultrasound. Fever or jaundice → Same-day biliary.
- Dyspepsia — no alarm features → H. pylori test or PPI. Exclude cardiac over 40, pancreatitis.
- Renal colic — loin to groin, haematuria → CT KUB ≤24 h (ultrasound if pregnant); fever, single kidney, pregnancy → emergency. Older: AAA first.
- PID → BASHH regimen + sexual health. IBS — positive diagnosis; 50+ or alarm features → tests first.
- Unclassified — say so; never default to “constipation”, “gastritis” or “IBS” → review 12–24 h
5Treat today — doses: NICE/SPC, BNF, local formulary
- Analgesia — give it; paracetamol first (max 4 g/24 h; less if low weight or liver disease). NSAID for renal or biliary colic unless GI bleed/ulcer, renal impairment, dehydration, heart failure, anticoagulation, pregnancy, CVD, frailty, ACE inhibitor + diuretic.
- Diverticulitis, well: consider no antibiotic, review 48 h. Unwell, immunosuppressed or comorbid: co-amoxiclav 500/125 mg TDS 5 days. Avoid NSAIDs and opioids where possible.
- Dyspepsia, no alarm features: stop NSAID; full-dose PPI 4 weeks, or H. pylori test and treat (2-week PPI washout first).
- Lower UTI, non-pregnant woman: nitrofurantoin 3 days, per local guidance. Men, pregnancy: 7 days + MSU.
6Refer routinely
- Symptomatic gallstones → upper GI surgery. Dyspepsia failing eradication and full-dose PPI, no alarm feature → gastroenterology.
- Raised calprotectin, positive tTG-IgA → gastroenterology. Chronic pelvic pain, endometriosis → gynaecology.
7Never reassure by
- A soft abdomen (ischaemia, AAA, ectopic).
- Normal temperature or bloods (early appendicitis, sepsis).
- Pain that has settled — including torsion.
- Normal bowel sounds.
- Contraception, without a pregnancy test.
- Mild signs in the old, diabetic or on steroids; a low FIT with a mass.
8Safety-net — say it, then document it
999 “Call 999 or go to A&E if the pain becomes severe or constant, your tummy goes hard, you vomit repeatedly, pass blood or black stools, faint or go cold and clammy, or get a fever with shivering.” Same day: “If the pain moves to one place or worsens over hours, or you get jaundice or a positive pregnancy test.”
Remote or OOH: convert to face-to-face or emergency if the abdomen, observations or a needed pregnancy test cannot be done; pain is severe, progressive or localising; vomiting stops drinking; over 65, frail, immunosuppressed or anticoagulated; or no reliable same-day review or safe transport.
✓Safe to leave primary care only if — all five, documented
No block 0–2 row applies
Observations normal; pregnancy test negative if relevant
Abdomen soft; groins and scrotum examined
One diagnosis explains it, NG12 considered — or 12–24 h review
Written safety-net; review booked, named owner
Summary of the full Reasoning GP abdominal pain algorithm, which holds the detail and evidence. Sources: NICE NG12 (updated April 2026), NG126, NG147, NG118, NG109, NG253, CG184, CG188, CG61, NG20, NG73; BASHH; MHRA. Clinical reference — follow local policies and check doses: NICE/SPC, BNF.