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19th July 2023
Classification
The most common and well-known functional bowel disorder is Irritable Bowel Syndrome (IBS), estimated to affect 10-20% of the UK population. However, there are other FBDs which are defined according to the Rome IV criteria, shown in table 5.
| Functional Bowel Disorder | Rome IV Diagnostic Criteria |
|---|---|
| Irritable Bowel Syndrome | Recurrent abdominal pain occurring at least 1 day per week + ≥2 of:
IBS Subclassification – based on the predominating Bristol Stool Type: IBS with predominant constipation (IBS-C): predominant tendency to constipation with firm stool IBS with predominant diarrhoea (IBS-D): predominant tendency to diarrhoea with loose stool IBS with mixed bowel habits (IBS-M): tendency to both diarrhoea and constipation IBS Unclassified (IBS-U): cannot be categorised into another group but meet IBS diagnosis |
| Functional abdominal bloating | Recurrent abdominal bloating and/or distension which predominates over other symptoms
Do not meet IBS criteria |
| Functional diarrhoea | Loose or watery stools without predominant abdominal pain or bloating
Do not meet IBS criteria |
| Functional constipation | Symptoms of constipation (straining, lumpy/hard stool, feeling of incomplete evacuation or anorectal obstruction/blockage, need for manual manoeuvres or laxatives to aid defecation, < 3 small bowel movements per week)
Do not meet IBS criteria |
| Opioid induced constipation | New or worsening symptoms of constipation when initiating, changing or increasing opioid therapy |
| Unspecified functional bowel disorder | Bowel symptoms that cannot be attributed to an organic aetiology but also do not meet diagnostic criteria for any of the other FBDs |
Table 5: The Rome IV Diagnostic Criteria of FBDs
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