Synopsis
Make a confident positive diagnosis of irritable bowel syndrome after proportionate exclusion of important disease, then deliver phenotype-led dietary, pharmacological and behavioural care with explicit safety-netting.
- IBS is a disorder of gut-brain interaction characterised by recurrent abdominal pain linked to defaecation or altered stool frequency or form, not a diagnosis defined by bloating alone.
- Classify the current pattern as constipation-predominant, diarrhoea-predominant, mixed or unclassified because treatment follows the dominant stool problem and can change over time.
- Make a positive diagnosis when the symptom pattern, examination and limited tests fit; repeated normal scans and colonoscopies can reinforce uncertainty rather than improve care.
Key red flags
Blood mixed with stool, night-time diarrhoea, fever, raised inflammatory markers, perianal disease or progressive weight loss is discordant and requires assessment for IBD, infection or microscopic colitis.
Investigation priorities
Look for anaemia and objective inflammation that would make uncomplicated IBS less likely.
Management branches
Recurrent abdominal pain and altered bowel habit suggest a disorder of gut-brain interaction.
- Map pain to defaecation and stool change, record Bristol form and duration, examine the abdomen and rectum when clinically indicated, and ask about warning features.
- Request full blood count, inflammatory markers and coeliac serology, adding calprotectin, infection testing, FIT or endoscopy only for a defined indication.
Typical IBS is established without a current red flag or untreated organic mimic.
Key medicines
LoperamideUse the current formulary starting regimen for IBS-D and let the patient titrate cautiously towards Bristol type 4 rather than a fixed maximal schedule.
Soluble fibre or laxativeIntroduce ispaghula or another suitable constipation treatment gradually with fluid, then adjust to a soft formed stool using the local formulary sequence.