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.


  • 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



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
WordPress Theme built by Shufflehound. Copyright 2016-2021 - Zero to Finals - All Rights Reserved