Core rule: persistent bloating in a woman is an ovarian cancer prompt, not "just IBS" — follow NG12 first. Bloating alone is not IBS, and IBS is diagnosed only once alarm features are excluded.
0Stop — act now — before any work-up
- Severe distension + absolute constipation + vomiting (large bowel obstruction) → Same-day surgical; 999 if unstable. Imaging by the hospital team.
- Peritonitis, or haematemesis in cirrhosis (variceal bleed) → 999
- Ascites with fever, abdominal pain, new confusion or unexplained deterioration (possible spontaneous bacterial peritonitis) → Same-day hospital
1Triage the woman — NG12 ovarian (updated April 2026)
Persistent or frequent (especially >12 times a month) bloating, early satiety, pelvic or abdominal pain, or urinary urgency or frequency; especially 50+.
| Finding | Action |
|---|---|
| On examination | Ascites, or a pelvic or abdominal mass (not obviously fibroids), on examination → Gynae suspected cancer pathway without waiting for CA125 |
| Aged 40+ | CA125 ≥35 IU/mL at 40–49 · ≥31 at 50–59 · ≥24 at 60–69 · ≥25 at 70–79 · ≥31 at 80+ → Urgent USS |
| Aged 39 or under | Do not use CA125 alone → consider Urgent USS |
| Results normal | Investigate other causes; safety-net if symptoms persist |
2Screen — one row is enough
- Colorectal: offer FIT for a mass, change in bowel habit or iron-deficiency anaemia; 40+ weight loss + abdominal pain; <50 rectal bleeding + pain or weight loss; 50+ bleeding, pain or weight loss; 60+ anaemia. FIT ≥10 µg Hb/g → Suspected cancer pathway
- FIT is triage, not rule-out: a mass, persistent bleeding, anaemia or progressive symptoms → refer despite a negative FIT.
- Ascites (shifting dullness, fluid thrill) → Urgent USS, LFTs, albumin, AFP; hepatology urgently. Woman → block 1.
- Woman 50+ with new IBS-type symptoms → NG12 CA125/USS before any IBS label.
- Diarrhoea, fatigue, anaemia, weight loss → coeliac serology; calprotectin only if IBD is realistic and cancer not suspected.
3Assess
☐ Alarm features: age >50, weight loss, bleeding, anaemia, nocturnal symptoms, family history (colorectal, ovarian) ☐ Foods, bowel habit, medicines, gynae history ☐ Examine standing: dullness, shifting dullness, masses, organomegaly, rectal; pelvic if appropriate ☐ FBC, ferritin, CRP/ESR, anti-tTG IgA + total IgA (eating gluten), TFTs, HbA1c as indicated. No SIBO breath tests or empirical rifaximin.
4Classify — only if the screen is negative
- IBS — ≥6 months of pain or discomfort related to defaecation or altered stool, + ≥2 supporting features (CG61), no alarm features → positive diagnosis; no test confirms it.
- Functional bloating — distension ± discomfort, no pain, IBS criteria not met.
- Dietary or swallowed air — reproducible after FODMAP foods, fizzy drinks, gum, eating fast.
- Constipation — hard stools ferment; treat it first.
- Coeliac or IBD — positive serology or raised calprotectin → gastroenterology. SIBO only with risk factors, via gastroenterology.
- Uncertain — do not label it IBS; re-check alarm features at review.
5Treat today — doses: NICE/SPC, BNF, local formulary
- Diet: regular meals; cut fizzy drinks, gum and gas-producing foods; soluble fibre (ispaghula), not bran. Treat constipation (macrogol).
- Probiotic if the patient wishes: one product for at least 4 weeks; stop if no benefit.
- IBS pain: mebeverine 135 mg TDS or hyoscine butylbromide 10 mg TDS (up to 20 mg QDS). IBS-D: loperamide 2 mg as needed.
- Not helped: consider low-dose amitriptyline 5–10 mg at night, not usually beyond 30 mg (CG61).
6Refer routinely
- Dietitian: low-FODMAP for IBS (not a leaflet), coeliac education, lactose intolerance.
- Gastroenterology: positive coeliac serology, raised calprotectin (local pathway), suspected SIBO or bile acid diarrhoea.
- Refractory IBS → consider gut-directed hypnotherapy or IBS-specific CBT (ask NHS Talking Therapies for IBS-focused).
- Review at 6–8 weeks; no better → step up (antispasmodic → low-dose TCA → referral).
7Never reassure by
- An IBS label for persistent bloating in a woman before the NG12 pathway.
- A normal CA125 — it does not exclude ovarian cancer.
- A negative FIT when there is a mass, bleeding, anaemia or progression.
- Calling new symptoms at 50+ "IBS".
- A normal calprotectin — it does not exclude all IBD.
- Bloating alone as proof of IBS.
8Safety-net — say it, then document it
999 “Call 999 if your tummy swells badly and you are vomiting and passing no wind or stool, you have severe constant pain, or you vomit blood.” Same day “If you have liver disease with fluid in the tummy and get a fever, tummy pain or new confusion, contact us today.”
Within 2 weeks “Come back if the bloating persists despite treatment, or you lose weight, notice bleeding, a change in your bowels or a lump.” Normal CA125 or USS: safety-net if symptoms persist.
✓Safe to leave primary care only if — all five, documented
No block 0–2 row applies; alarm features asked
Woman: NG12 CA125/USS done or not indicated
Examined: no ascites, mass or organomegaly
FBC, coeliac serology, CRP and FIT as indicated
Review at 6–8 weeks booked; safety-net given
Summary of the full Reasoning GP bloating algorithm, which holds the detail, IBS subtypes, ascites work-up and evidence. Sources: NICE NG12 (updated April 2026), CG61, NG20, HTG690, HTG320, NG50; BSG IBS (2021) and ascites (2020) guidelines. Clinical reference — follow local pathways and check doses: NICE/SPC, BNF.