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Irritable Bowel Syndrome – Overview

Patient Information

Irritable Bowel Syndrome

Patient information

Definition of IBS

IBS is the most common GI disorder seen in clinical practice. Irritable bowel syndrome (IBS) is a gastrointestinal disorder characterized by chronic abdominal pain and altered bowel habits in the absence of any organic disorder. Symptoms may include bloating, diarrhea or constipation. The nature and severity of symptoms vary widely between patients and may vary with time.


Currently it is useful to classify irritable bowel syndrome into several subtypes according to clinical presentation. These are useful for guiding the approach to therapy. These are:

  • C-IBS  constipation predominant
  • D-IBS  diarrhoea predominant
  • A-IBS  alternating predominant
  • C-IBS is defined as abdominal pain or discomfort that may be relieved by defaecation and is associated with < 3 bowel actions/week for at least 1 in 4 weeks and hard or lumpy stools on at least 1 in 4 bowel actions.
  • D-IBS is defined as abdominal pain or discomfort that may be relieved by defaecation and is associated with > 3 bowel actions/day for at least 1 in 4 weeks and loose or watery stools on at least 1 in 4 bowel actions or days.

Suspect IBS when a patient reports chronic recurrent abdominal pain and constipation or diarrhoea and bloating and is otherwise healthy.


90% of the human bodies seretonin is contained in the gastrointestinal tract. Seretonin has been implicated in the altered motor and sensory function observed in irritable bowel syndrome. 5HT4 and 5HT3 receptors are the major seretonin receptors in the bowel. Activation of 5HT3 receptors leads to improvement in:

  • Gut secretion
  • Colonic motility
  • Peristalsis
  • Sensory function

Lifestyle Advice

A good doctor patient relationship is integral to the management of IBS. This includes counselling about the disease entity of IBS and reassurance of the benign nature of IBS which will help the patient’s self esteem and relieve anxiety. In addition, a healthy balanced diet and lifestyle is always of benefit in the long- term management of IBS.

This includes:

  • stress management
  • sleep, recreation time
  • regular meals and exercise
  • plus regular meals including fibre, water and reduced fat, sugar

The aim with dietary fibre supplementation is to start low and go slow as too much fibre will often lead to excessive bloating in C-IBS. The aim  is 20g daily of soluble fibre.

  • Soluble fibre (smooth) is partially digested by colonic bacteria and thus will yield gas but prevents diarrhoea and abdominal cramps.
  • Insoluble fibre (rough) is not broken down by colonic bacteria thus reduces bloating but can lead to diarrhoea and abdominal cramping.

Fibre Sources and Supplements

Soluble Fibre:

  • Natural – oat bran, psyllium, rice, potato.
  • Commercial – Metamucil/ nucolox, – psyllium, normacol  – sterculia, fybogel – ispaghula, agiofibe – psyllium/ispaghula,  easyfibre – maltodextran

Insoluble Fibre:

  • Natural – wheat bran, celery, corn, raw greens, apples, carrots
  • Commercial – easyfibre – methylcellulose

Foods to Avoid for Bloating:

The normal colon contains around 200ml of bowel gas. However certain foods can lead  to excess production of gas by colonic bacteria related to their sugar content.

  • Raffinose – baked beans, cabbage, brussel sprouts, broccoli, carrots
  • Fructose – onions, pears, artichokes, bananas, raisins
  • Sorbitol – apple, peach, pear, prune, apricot,  artifical sweeteners
  • Lactose – milk, butter, cream, cheese
  • Starches – potato, corn, noodles, wheatgerm, bagels

Natural laxatives may be useful – licorice,  rhubarb,  prunes, figs and fresh fruit.