Irritable Bowel Syndrome

Irritable bowel syndrome is a “functional bowel disorder”. This means that there is no identifiable organic disease underlying the symptoms. The symptoms are a result of the abnormal functioning of an otherwise normal bowel.

It used to be described as a “diagnosis of exclusion”, however this term is not used any more. The idea was that this was a diagnosis that could only be made when other pathology had been excluded, however there has been a shift towards making a firm diagnosis based on clinical symptoms. Despite this, it is always important to keep other possible diagnoses in mind, particularly where there are red-flags such as rectal bleeding or a change in bowel habit in an older adults.

It is very common and occurs in up to 20% of the population. It affects women more than men and is more common in younger adults.

Symptoms

  • Diarrhoea
  • Constipation
  • Fluctuating bowel habit
  • Abdominal pain
  • Bloating
  • Worse after eating
  • Improved by opening bowels

 

Criteria for Diagnosis (NICE Guidelines)

Other pathology should be excluded:

  • Normal FBC, ESR and CRP blood tests
  • Faecal calprotectin negative to exclude inflammatory bowel disease
  • Negative coeliac disease serology (anti-TTG antibodies)
  • Cancer is not suspected or excluded if suspected

 

Symptoms should suggest IBS:

Abdominal pain / discomfort:

  • Relieved on opening bowels, or
  • Associated with a change in bowel habit

AND 2 of:

  • Abnormal stool passage
  • Bloating
  • Worse symptoms after eating
  • PR mucus

 

Management

Making a positive diagnosis and providing reassurance that there is no serious pathology present is important.

General healthy diet and exercise advice:

  • Adequate fluid intake
  • Regular small meals
  • Reduced processed foods
  • Limit caffeine and alcohol
  • Low “FODMAP” diet (ideally with dietician guidance)
  • Trial of probiotic supplements for 4 weeks

 

First Line Medication:

  • Loperamide for diarrhoea
  • Laxatives for constipation. Avoid lactulose as it can cause bloating. Linaclotide is a specialist laxative for patients with IBS not responding to first-line laxatives
  • Antispasmodics for cramps e.g. hyoscine butylbromide (Buscopan)

 

Second Line Medication:

  • Tricyclic antidepressants (i.e. amitriptyline 5-10mg at night)

 

Third Line Medication:

  • SSRIs antidepressants

 

Cognitive Behavioural Therapy (CBT) is also an option to help patients psychologically manage the condition and reduce distress associated with symptoms.

 

Last updated February 2019
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