Irritable bowel syndrome (IBS)

Discuss IBS?

  • IBS is a chronic, relapsing and often lifelong disorder
  • IBS patients present with varying symptom profiles, most commonly ‘diarrhoea predominant’, ‘constipation predominant’ or alternating symptom profiles.
  • IBS commonly affects people between the ages of 20 and 30 years.
  • IBS is twice as common in women as in men.
  • Prevalence in the general population is estimated to be between 10% and 20%.

Discuss the diagnosis of IBS?
The diagnosis of IBS is based on ROME III criterion. The criteria should be fulfilled for the last 3 months with symptom onset at least 6 months prior to diagnosis.
A positive diagnosis of IBS can be made by using ROME III criteria:
Recurrent abdominal pain or discomfort at least 3 days per month in the last 3 months associated with 2 or more of the following:

  • Improvement with defaecation
  • Onset associated with a change in frequency of stool
  • Onset associated with a change in form/appearance of stool

NICE recommends a positive diagnosis of IBS based on
Consider diagnosing IBS only if the person has abdominal pain or discomfort that is:

  • relieved by defaecation, or
  • associated with altered bowel frequency or stool form and at least two of the following:
  • altered stool passage (straining, urgency, incomplete evacuation)
  • abdominal bloating (more common in women than men), distension, tension or hardness
  • symptoms made worse by eating
  • passage of mucus.

Lethargy, nausea, backache and bladder symptoms are common in IBS and may be used to support diagnosis.

Discuss the investigations for suspected IBS?

All patients who met the diagnostic criterion for IBS should have

  • Full blood count (FBC)
  • ESR or plasma viscosity
  • C-reactive protein (CRP)
  • Coeliac serology.

The following tests are not needed to confirm a diagnosis of IBS:

  • Ultrasound
  • Rigid/flexible sigmoidoscopy
  • Colonoscopy; barium enema
  • Thyroid function test
  • Faecal ova and parasite test
  • Faecal occult blood
  • Hydrogen breath test (for lactose intolerance and bacterial overgrowth).

Discuss the symptoms (red flag indicators) that warrant further investigations?

  • unintentional and unexplained weight loss
  • rectal bleeding
  • family history of bowel or ovarian cancer
  • in people aged over 60, a change in bowel habit lasting more than 6 weeks with looser and/or more frequent stools
  • anaemia
  • abdominal masses
  • rectal masses
  • Raised inflammatory markers (suggestive of IBD).

Discuss the management of IBS?

Treatment for IBS is individualized on the basis of the type and severity of symptoms.
Dietary advice should be offered to all
First line treatment- single or in combination are antispasmodics, laxatives and loperamide.
Second line treatment- Tricyclic antidepressants, SSRI
Third line treatment- cognitive behavioural therapy (CBT), hypnotherapy, psychological therapy.

Specific diets or elimination diets have not been proven effective.

  • Have regular meals and take time to eat.
  • Avoid missing meals or leaving long gaps between eating.
  • Drink at least eight cups of fluid per day, especially water or other non-caffeinated drinks such as herbal teas.
  • Restrict tea and coffee to three cups per day.
  • Reduce intake of alcohol and fizzy drinks.
  • Consider limiting intake of high-fibre food (for example, wholemeal or high-fibre flour and breads, cereals high in bran, and whole grains such as brown rice).
  • Reduce intake of ‘resistant starch’ (starch that resists digestion in the small intestine and reaches the colon intact), often found in processed or re-cooked foods.
  • Limit fresh fruit to three portions (of 80 g each) per day.
  • For diarrhoea, avoid sorbitol, an artificial sweetener found in sugar-free sweets (including chewing gum) and drinks, and in some diabetic and slimming products.
  • For wind and bloating consider increasing intake of oats (for example, oat-based breakfast cereal or porridge) and linseeds (up to one tablespoon per day).
  • Moderation in fat intake is reasonable, since lipids amplify gut sensations and motor reflexes.
  • In patients with symptoms of bloating or flatulence, avoiding beans, cabbage, and uncooked broccoli and cauliflower may help.


Exercise has been associated with improved outcomes in uncontrolled studies and is reasonable as a general recommendation.

Fiber supplements

Controlled trials suggest that fiber supplements are effective for the constipation symptoms of irritable bowel syndrome, but not for pain or diarrhea.
Some patients who take fiber, particularly those with diarrhea-predominant irritable bowel syndrome, have worsening of symptoms. Intake of insoluble fibre (like bran) should be discouraged. If more fibre is needed, recommend soluble fibre such as ispaghula powder, or foods high in soluble fibre (for example, oats).

Treatment of constipation

  • Fiber supplements- it is less likely to work for constipation in those with very slow colonic transit.
  • Long-term use of an osmotic laxative is effective and safe in severe constipation. Magnesium salts, phosphate salts, and polyethylene glycol (PEG)–based laxatives (PEG- movicol 1-3 sachets daily) are effective and tachyphylaxis is rare.
  • Lactulose is effective but can worsen bloating.
  • Stimulant cathartics such as bisacodyl and senna can cause cramping and are associated with both tachyphylaxis and dependency. Long term use of stimulant cathartics should be avoided.
  • Docusate probably acts both as stimulant and as softening agent.

Treatment of diarrhea

  • Diphenoxylate–atropine (opiod analogue)
  • Loperamide- preferable for long-term use because it is available without prescription, does not have an anticholinergic component, and does not induce euphoria at any dose.
  • Cholestyramine -A bile-acid binder. It may be added empirically to control refractory diarrhea.

Abdominal pain

  • Data from randomized trials indicate that antispasmodic agents decrease global symptoms and reduce pain. Antispasmodic agents relax the smooth muscle of the gut or reduce its contractility. Antispasmodic agents taken 30 minutes before meals can substantially inhibit the gastro-colic reflex, reducing postprandial urgency and cramps.
  • Common but generally mild and rapidly reversible side effects of anticholinergic antispasmodic agents include dry mouth, blurred vision, fatigue, and urinary hesitancy. Narrow-angle glaucoma and urinary retention are contraindications.
  • Antispasmodic agents- Hyosine (Buscopan 20mg QDS), Dicyclomine 10mg 4 times daily, Mebeverine 135–200 mg TDS (Colofac 135mg TDS, colofac MR 200 BD). These should be used on a prn basis
  • Peppermint oil (colpermin 1-2 caps tds) appears to have direct relaxing effects on GI smooth muscle.

Tricyclic antidepressants

Tricyclic antidepressants are recommended for moderate-to-severe IBS in which pain is prominent or when other therapies have failed. Benefits are seen within two weeks.  A number of RCT’s have demonstrated decreased symptoms in patients taking low-dose tricyclic antidepressants such as amitriptyline, desipramine, clomipramine, doxepin, and trimipramine.  Side effects include constipation, fatigue, somnolence, dry mouth, and urinary retention.   Since somnolence may occur, the drugs should be taken at bedtime. Daily administration starting at a dose of 10 to 25 mg for any of the tricyclic antidepressants, with a gradual escalation to a dose of 25 to 100 mg, is suggested.   Tricyclic antidepressants may be continued for 6 to 12 months, after which an attempt to taper the dose should be made.

Selective serotonin-reuptake inhibitors do not have the same anti nociceptive effects as tricyclic antidepressants and have yet to be proved effective for irritable bowel syndrome or any other functional gastrointestinal disorder.  Although evidence to support its use is lacking, this class of drug may also be tried if a tricyclic antidepressant fails.

Psychotherapy is useful for selected patients with severe IBS. Diarrhea and pain appear to respond to psychotherapy, whereas constipation does not. A variety of psychotherapy techniques, including cognitive behavioral therapy (directed at maladaptive perceptions of illness and behavior), dynamic psychotherapy (directed at interpersonal problems), relaxation therapy, and hypnotherapy, alone or in combination, are reportedly effective for symptoms.

Discuss other therapies for IBS?

Serotonin-3 receptors antagonist- Alosetron
Serotonin is released by GI entero endocrine cells stimulates peristalsis by binding to serotonin- 3 and serotonin-4 receptors located on enteric nerves. Alosetron reduces diarrhea and urgency. It can cause ischaemic colitis and was withdrawn from the market by the manufacturer. However it is still available on a named patient basis. Given its known side effects, alosetron therapy should be limited to women with irritable bowel syndrome without constipation who have symptoms severe enough to justify the risk of drug-induced ischemic colitis and who have had no response to other therapy.

Serotonin-4–receptor agonists- Tegaserod
Tegaserod is approved by the FDA for use for up to 12 weeks in women with constipation-predominant irritable bowel syndrome. Given its cost and its relatively moderate advantages over placebo, tegaserod should be reserved for female patients with constipation-predominant IBS pain who have no response to fiber or laxatives and antispasmodic agents.
Both alosetron and tegaserod are not available in UK.


  1. NICE guidance

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