Irritable Bowel Syndrome

Background

• Chronic, relapsing disorder of GI function (no structural or biochemical cause); characterised by:
  • Presence of abdominal pain/discomfort associated with, or relieved by, defaecation
  • A change in bowel habit
  • Abdominal bloating
• The cause of IBS is unknown (possible abnormal motility, hypersensitivity/immune dysregulation; abnormal autonomic activity/CNS modulation
• Occurs in around 10-20% of the general population at some point but only 10% of these will go to the doctor
  • Still most common cause of GI referral and a big cause of sick days/impaired quality of life caused by GI disorder
  • More common in women; often young (20-30); and often associated with other functional disorders e.g. non-ulcer dyspepsia; chronic fatigue; primary dysmenorrhoea and fibromyalgia
    • There may also be mood problems/psychiatric history (including physical/sexual abuse)
• NB Any patient >60 with a change in bowel habit lasting >6 weeks should be referred for investigation of colorectal cancer

Clinical Presentation/Diagnosis

• Consider IBS in a patient with the 3 classical features (above) for >6 months
• Diagnosis is suggested if
  • Discomfort/pain is relieved by defecation or associated with altered bowel frequency/form; AND 2 of:
    • Altered stool passage (straining, urgency, incomplete evacuation)
    • Abdominal bloating; distension; tension or hardness
    • Symptoms made worse by eating
    • Passage of mucus
  • IMPORTANT- where other causes have been ruled out e.g. IBD
• Other features may include
  • lethargy, nausea, backache, headache, urinary symptoms; features of depression/anxiety
• It is important to exclude other causes- ask about red flags
  • blood in stools, weight loss, night sweats, anorexia, pallor
  • Look for any abdominal masses
  • You may also want to perform a PR exam to rule out any rectal masses
  • Ask about family history or other concerns

Investigations

• Rule out other potential causes with
  • FBC, U&Es; ESR/PV; CRP; Anti-endomysial antibodies or tissue transglutaminase antibodies (Coeliac screen)
  • If abnormal, further investigation for another cause should be sought 

Management

• Advice on avoiding food triggers, stress, food routine, healthy and balanced diet, decent fluid intake etc
  • Also exercise
• For abdominal spasms/pain, consider mebeverine
• For constipation, consider a laxative (bulk forming preferred e.g. ispaghula; alternatives include movicol or senna (short term)
  • NOT lactulose
• For diarrhoea, consider antimotility drug e.g. loperamide
• If symptoms do not improve, consider a tricyclic antidepressant e.g. amitrityline (5-10mg nocte initially and titrate up as necessary)
• Consider other antidepressants (SSRIs) if there are features of depression

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