IBS and IBD

IBS

Also called: irritable bowel syndrome, spastic colon

IBS stands for irritable bowel syndrome. It is a long-term gut condition that causes recurring abdominal pain alongside altered bowel habits, without visible damage to the gut. It affects roughly 1 in 10 UK adults at any given time. The cause is not single. It involves gut motility, gut sensitivity, the microbiome, the nervous system, and how the brain processes gut signals.

The three subtypes

  • IBS-D: diarrhoea-predominant. Loose stools more than 25 percent of the time, hard stools less than 25 percent.
  • IBS-C: constipation-predominant. Hard stools more than 25 percent of the time, loose stools less than 25 percent.
  • IBS-M: mixed. Both loose and hard stools more than 25 percent of the time. The most variable subtype to manage.

How IBS is diagnosed

IBS is diagnosed using clinical history, not by a positive test. The current Rome IV criteria require recurrent abdominal pain at least one day a week in the last three months, alongside two or more of: pain related to defaecation, change in stool frequency, or change in stool form. NICE in the UK recommends ruling out coeliac disease (with a blood test) and inflammatory bowel disease (often with faecal calprotectin) before settling on IBS.

Common triggers

  • FODMAPs. Wheat, onion, garlic, lactose, apples, pears, beans, mushrooms.
  • Stress and anxiety. The gut-brain axis is heavily involved.
  • Hormonal cycle changes. Symptoms often worsen in the luteal phase.
  • Caffeine and alcohol.
  • Disrupted sleep, especially shift work patterns.
  • Some food poisoning episodes can trigger post-infectious IBS that lasts months or years.

First-line management in the UK

NICE Clinical Guideline 61 sets out the standard pathway. It starts with general dietary and lifestyle changes: regular meals, slower eating, adequate fluid, limited caffeine and alcohol, and adjusting fibre intake. If symptoms persist, the second-line dietary intervention is a low-FODMAP diet under a registered dietitian. Antispasmodics like mebeverine, peppermint oil capsules, and bowel-specific laxatives (for IBS-C) or low-dose loperamide (for IBS-D) are common medications. Cognitive behavioural therapy and gut-directed hypnotherapy have evidence and are recommended for moderate-to-severe IBS.

Newer options

Linaclotide is a UK-licensed drug for moderate-to-severe IBS-C. Eluxadoline is licensed for IBS-D in some settings. Rifaximin, an antibiotic that stays largely in the gut, is sometimes used in IBS-D where SIBO is suspected. Specific probiotic strains have evidence for some IBS subtypes. Continuous food and symptom tracking, including with wearables, is a developing area of research.

When the symptoms are not IBS

Some signs are not consistent with IBS and need urgent assessment: blood in stool, unintentional weight loss, persistent night-time symptoms that wake you up, persistent fever, anaemia, or a strong family history of bowel cancer. NHS guidance is to see a GP without delay if any of these are present.

Common questions

How is IBS different from IBD?
IBS is a functional condition. The gut behaves abnormally but does not show damage on imaging or biopsy. IBD (Crohn's disease, ulcerative colitis) involves visible inflammation and tissue damage. IBD is typically diagnosed with colonoscopy and biopsies. The two can co-exist.
Can IBS go away on its own?
Some people experience long periods of remission, especially after addressing stress or removing trigger foods. Others have lifelong fluctuating symptoms. The goal of treatment is symptom control and quality of life rather than cure.
Is the low-FODMAP diet a cure for IBS?
No. Around three in four people with IBS see meaningful improvement on a properly-followed low-FODMAP elimination phase. The diet is not a cure: stopping it returns most people to their previous state. The point is to identify personal triggers and personalise long-term eating.
How long does an IBS flare last?
Acute flares typically last hours to a few days. Longer-term flare periods can last weeks. If a flare lasts more than three weeks without improvement, see a GP. New persistent symptoms are not always IBS.

Sources