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.
- Fluctuating bowel habit
- Abdominal pain
- 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
- 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