Irritable bowel syndrome - Disorders of the large bowel and inflammatory bowel disease

Irritable bowel syndrome

Definition

A condition of disordered lower gastrointestinal function in the absence of known pathology of structure.

Prevalence

Common, affecting ∼10% of the population.

Age

Any

Sex

1M : 2F

Aetiology/pathophysiology

50% of patients seen in gastroenterology clinics attribute the onset of their symptoms to a stressful event including physical or sexual abuse as child or adult. Patients have a higher incidence of psychological symptoms, psychiatric disease and other somatic complaints.

10–20% of patients relate the onset of their symptoms to an acute gastrointestinal illness. Food allergy is rare but many patients believe that certain foods exacerbate symptoms. There is no consistent evidence of abnormal motility.

Some patients with irritable bowel syndrome exhibit evidence of altered CNS processing of visceral pain.

Clinical features

Patients complain of recurrent abdominal pain, most often in the left iliac fossa, associated with disturbed bowel habit (including the passage of mucous). There is often a sensation of bloating and the frequent passage of small volume stool, which may relieve discomfort. Non-gastrointestinal symptoms include lethargy, poor sleep, generalised aches and pains. Examination is unremarkable.

Investigations

Investigation is required if there is weight loss, rectal bleeding, nocturnal symptoms, anaemia or an atypical history particularly in older patients. Investigation may include flexible sigmoidoscopy, with colonoscopy/barium enema in patients with onset of symptoms over the age of 45 years.

Management

Psychological support and reassurance is essential. Coexistent psychological disorders should be identified and treated; relaxation therapy, biofeedback training and cognitive behavioural therapy may be of benefit.

A sensible balanced diet avoiding food fads and excessive caffeine.

Antispasmodics may help, e.g. hyoscine butylbromide, mebeverine. Alternatively a tricyclic antidepressant

can be tried. Urgency and diarrhoea can be treated with loperamide or codeine, whereas constipation can be helped by increased soluble fibre intake.