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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