Irritable bowel syndrome

What is irritable bowel syndrome

• a functional bowel disorder in which abdominal pain is associated with defecation

or a change in bowel habit, with features of disordered defecation and distention

• prevalence 5-25%

• male = female, except female predominance in those seeking medical attention

and in constipation-dominant IBS

What are the criteria to diagnose irritable bowel syndrome

Manning criteria

• Pain relieved by defecation

• More frequent stools at the onset to pain

• Looser stools at the onset of pain

• Visible abdominal distention

• Passage of mucus

• Sensation of incomplete evacuation

Rome III criteria

Recurrent abdominal pain or discomfort** at least 3 days/month in the last 3 months associated with two or more of the following:
1. Improvement with defecation
2. Onset associated with a change in frequency of stool
3. Onset associated with a change in form (appearance) of stool
* Criterion must be fulfilled for the last 3 months with symptom onset at least 6 months prior to diagnosis
** “Discomfort” means an uncomfortable sensation not described as pain.

What is the pathogenesis of irritable bowel syndrome

• biopsychosocial disorder

• abnormal motility (, or disordered)

• heightened visceral perception - peripheral or central

• psychological distress

• intraluminal factors irritating small bowel or colon (lactose, other sugars, bile

acids, short-chain fatty acids, food allergens)

• post-infectious neuro-immune modulation of gut functions

What is the approach to IBS

• history

• positive features of IBS

• exclude organic disease (weight loss, PR blood)

• investigation / exclusion of significant pathology

• FBC, ELFT, ESR (organic disease)

• stool culture

• colonoscopy

• therapeutic trial (depending on predominant symptoms- pain, diarrhoea,

constipation, bloating)

• fibre

• laxatives

• antispasmodics

• hyoscine – Buscopan

• mebeverine – Colofac

• tricyclic antidepressant (diarrhoea with pain)

• antidiarrhoeals (loperamide)

• cholestyramine

• Zelmac – constipation predominant IBS in females, 5HT-4 partial agonist

• further investigation if therapeutic trial fails

• colonic transit studies

• defaecation studies

• lactose-hydrogen breath test

• small bowel series to exclude obstruction

• experimental agents

• 5HT-3 antagonists

• 5HT-4 partial agonist (tegaserod – Zelmac – constipation predominant

IBS in females)

• K-opioid agonists (fedotozine)

• NK antagonists

What is loperamide

• synthetic opioid that does not cross the blood-brain barrier

• 2-4mg up to 4 times daily

• actions

• decreases intestinal transit time

• increases water and ion absorption

• increases tone of the internal anal sphincter