Irritable bowel syndrome

Irritable bowel syndrome (IBS) is the commonest of the functional gastrointestinal disorders (FGIDs). Its key presenting features are recurrent abdominal pain and change in bowel habit (diarrhoea and/or constipation), which may be severe, such that for an individual, there may be a marked negativity on quality of life, and for the population, a major social and economic burden.

Epidemiology

Irritable bowel syndrome is common, with research showing a prevalence as high as 20%, the wide variability related to the area of the world studied and the diagnostic criteria employed.

Clinical presentation

The two central characteristics are episodic abdominal pain and a change in bowel habit:

• recurrent abdominal pain
• change in bowel habit (CBH)
  • diarrhoea (IBS-D)
    • 50% mucus discharge
  • constipation (IBS-C)
  • alternating diarrhoea and constipation (IBS-M)
  • opening of the bowels usually occurs after a bout of lower abdominal colicky pain
• post infectious IBS
  • subdivision of IBS-D patients who experience the presentation following an episode of acute infective enterocolitis
• other GI manifestations
  • abdominal bloating
  • difficulty in swallowing
  • early satiety
  • episodic heartburn
  • nausea 
  • chest pain (non-cardiac)

Diagnosis of irritable bowel syndrome may be difficult and rests upon the Rome criteria, now in their fourth iteration, i.e. "Rome IV".

It is not unusual for patients to have other co-existing functional gastrointestinal disorders, e.g. functional dyspepsia, which is thought to be related to the underlying, poorly-understood common pathogenic processes of these functional disorders.

Pathology

Aetiology

The cause of irritable bowel syndrome remains unknown, despite much research effort to elucidate its aetiology. This usually suggests that multiple factors are at play. Recently a ubiquitous protozoan called Blastocystis sp. has been implicated as a risk factor. The exact mechanism through which it may cause IBS is not known.

History and etymology

Irritable bowel syndrome was first described in the literature over 150 years ago by W Cumming, and it is revealing that despite numerous advances since then the condition remains very puzzling in its causation ³.