Irritable Bowel Syndrome (IBS)

What is Irritable Bowel Syndrome?

Irritable bowel syndrome (IBS) is one of the most common digestive health disorders, affecting 10-15% of the Australian population. It is a condition characterised by gut-related symptoms including pain, bloating and a change in bowel habit. For some IBS is just a mild annoyance but for others it can be quite disabling. Unfortunately, it is often undertreated with many patients continuing to experience long-term problems. It does not cause permanent harm to the bowel or to a serious disease such as cancer.

What causes Irritable Bowel Syndrome?

The bowel is a muscular tube which moves food to the anus allowing nutrients to be digested and absorbed along the way. The large intestine (colon) links the small bowel to the rectum and anus and is the source of most of the symptoms of IBS. The nerves in the bowel are responsible for the sensations we feel in the abdomen and they coordinate the contractions of the muscles of the bowel. The exact cause of IBS is still debated, with a large amount of research still ongoing. Several factors that play a major role include:

  1. Digestive bacterial imbalance (gut dysbiosis)

 There are 100 trillion bacteria living in our digestive tract. There are 300-500 different species of bacteria living in our gut at any particular time (1). With 10 trillion cells in our body, we have more bacteria in our gut than we have cells in our body. Our gut microbiome plays an important role in the function of the digestive tract and a disturbance in this population can lead to IBS symptoms. The focus of dysbiosis testing and treatment include:
a. Good vs bad bacteria and is the focus of probiotic and faecal transplant treatments.
b. Location and concentration of the bacteria: small intestinal bacterial overgrowth (SIBO) is an overconcentration bacterium in the first part of the small bowel. Overgrowth of bacteria can impair absorption of food from the small bowel as well as ferment foods leading to bloating. SIBO testing in patients with IBS symptoms was recommended in recently published guidelines (2)

  1. Gut sensitivity

The nerves of colon of a person with IBS is more sensitive and reactive than usual, so it responds strongly to stimuli that would not bother most people. Ordinary events such as eating and bowel distension from gas and other material in the colon can cause the colon to overreact in a person with IBS.

We know that a person with IBS has a bowel that is extra sensitive to distension/stretching (visceral hypersensitivity) and therefore experience more discomfort. When food that contains certain carbohydrates (FODMAP group of foods) are fermented in the large intestine, gas is produced. They also  draw water into the large intestine. The gas and water causes the intestine to expand/stretch causing discomfort. A low FODMAP diet reduces the gas production and the amount of water in the intestine resulting in less distension/stretch of the colon which improves IBS symptoms.


  1. Gut-Brain axis

 Outside of the brain, the digestive tract contains the second largest collection of neurons in our body. There is constant communication from the digestive tract to the brain and back through the vagus nerve and the spinal cord. The digestive tract is an important source of the production of neurotransmitters involved in the regulation of our mood (90% of the body’s serotonin and 50% of the body’s dopamine). Stress in our lives affects both our central nervous system (e.g. headaches) and the function of the nerves in our digestive system (e.g. abdominal cramping and spasms). IBS is not caused by stress and anxiety but they can make symptoms of IBS worse.

  1. Exaggerated Gastro Colic Reflex

This reflex is triggered when we eat to make room for the food just eaten The reflex causes the gut, predominantly your large intestine to contract and move the content in the bowel along. This reflex is often the reason people feel the need to open their bowel shortly after a meal. People with IBS often have a heightened gastro- colic reflex which means the bowel contract more strongly causing IBS symptoms. Eating a large meal or very fatty meal or drinking a large cold drink quickly may also trigger this reflex

  1. Infections

It up to 25% of cases IBS follows  an attack of gastroenteritis. The infection releases toxins that can damage nerve fibres in the gut, the nerve damage may persist even after the infection clears, leading to disordered muscular contractions of the bowel.

  1. Abnormal gut motility

Motility is to the movement of the gut. A large proportion of people with IBS have abnormal motility (the co-ordinations of the muscles of the bowel are abnormal) in a part of their gastrointestinal tract. It either contracts and moves too quickly leading to diarrhoea (IBS-D) or too slowly causing constipation (IBS-C).

  1. Food intolerances –The types of food we eat can also play an important role in how well our digestive tract functions and whether we experience any symptoms. Recent research performed in Melbourne has identified eating high levels of poorly absorbed fermentable carbohydrates (FODMAPs) can contribute significantly to IBS symptoms. The foods we eat can also influence the types and location of bacteria in the digestive tract (this is the science of pre-biotic therapies). Lactose and fructose are two of these types of sugars that often contribute to food intolerances. Chemicals in processed foods may also play a role.
iirritable-bowel-syndrome-ibs (Brain)

What are the symptoms of Irritable Bowel Syndrome?

While irritable bowel syndrome might not be a life-threatening condition, the symptoms can be quite debilitating. For some people it can have a dramatic impact on their quality of life impacting both their professional and social functioning. It is important to realise that normal bowel function varies from person to person.

The main symptoms of IBS are:
(i) abdominal pain – The pain is frequently described as cramping in nature and worse after a meal. Nausea often follows the pain and can last for hours. Often having a bowel movement can help relieve the pain.

(ii) Altered bowels habit -the consistency and frequency of the stools are also a main feature in IBS. Some people will have an intermittence between constipation and diarrhoea (IBS-Mixed), others mostly diarrhoea (IBS-D), and others a predominance of constipation (IBS-C).

(iii) bloating
(iv) changes in bowel habit (diarrhoea or constipation or both).

(v) flatulence – flatus is produced by the gut bacteria in the colon. Foods that are not fully digested by the time they get to the colon (like baked beans) are eaten by the gut bacteria and the by-product they release is gas.

Symptoms not consistent with IBS include rectal bleeding and weight loss.

How do you diagnose Irritable Bowel Syndrome?

The diagnosis of IBS is made through as careful clinical assessment and physical examination. Symptoms are compared to the internationally recognized Rome IV criteria for IBS.

One of the most important aspects of a diagnostic assessment for IBS is to rule out other diseases that may present with similar symptoms. These can include inflammatory bowel disease, a chronic gut infection, coeliac disease and cancer to name a few.

This diagnostic assessment may include blood and stool tests, a gastroscopy +/- colonoscopy, and imaging of the abdomen (ultrasound, CT scan, MRI). These tests are strongly recommended in the presence of any “alarm symptoms” which include:
-Bright blood in the stools (especially if mixed into the stools)
-Black stools (digested blood – likely bleeding from high up in the digestive tract)
-Unexplained/unintentional weight loss
-Bowel movements that wake you up in the middle of the night
-Recurrent fever/chills/night sweats

If IBS is confirmed, a look for the underlying cause of IBS is worthwhile:
– Assessing for an imbalance / overgrowth of gut bacteria can be helpful. Small intestinal bacterial overgrowth (SIBO) can be assessed by performing a lactulose breath test.
– A food diary with digestive symptoms should also be started. This is the first step in identifying food intolerance.

How do you treat Irritable Bowel Syndrome?

The treatment of IBS has many different options.  Often, more than one treatment will be required to alleviate symptoms and this will depend on the type of IBS and its associated symptoms:

  • Diet – As food is often a major trigger of symptoms, a consultation with a dietitian experienced in IBS can be very helpful. The diet in IBS that has the most evidence for symptom relief was created here in Australia.  It is called the low FODMAP diet.  It involves removing all poorly absorbed fermentable carbohydrates for a period of 6 weeks and then systematically reintroducing certain foods in order to identify specific triggers. Alcohol can irritate the gut in some people. Consider your alcohol intake if excessive as part of your management plan for IBS.


  • Exercise: – affects the function of the Gastrointestinal tract. During exercise the bowel often quietens down. Doing some regular exercise is useful to reduce the symptoms of IBS.


  • Antibiotics – If you test positive for SIBO, a short course of antibiotics followed by a specific diet (SIBO diet) is recommended.  The antibiotic most commonly used to treat SIBO is Rifaximin (Rx) as it is the antibiotic with the most evidence in SIBO and has minimal absorption into the body (remains in the gut).


  • Fiber and laxatives – a bulk-forming soluble fiber such as Normofibe can help both diarrhoea and constipation .It is likely to cause less bloating compared with psyllium husk and Metamucil.  Laxatives such as PEG 3350 (Movicol or Osmolax) (OTC), Lactulose (OTC), coloxyl (OTC) and glycerine suppositories (OTC) are recommended for mild to moderate constipation. Prucalopride (Restotrans) (Rx) is a medication designed to stimulate the bowel and is used for refractory constipation.


  • Herbal supplements – there are several on the market including Kivia (kiwifruit extract – OTC). Mintec 9peppermint oil capsules) may help symptoms of IBS.


  • Anti-diarrhoeal medications – including Loperamide (OTC) and Lomotil (Rx)may be effective in IBS-C.


  • Anti-spasmodics – for the treatment of abdominal cramping: Iberogast (OTC), Mebeverine (Colofac) taken regularly three times a day (Rx), Hyoscine (Buscopan) (Rx).


  • Antidepressants – certain antidepressants can be used in low doses to treat IBS. They have a separate effect on the nerves and muscles in the bowel and can be helpful in relieving pain.


  • Gut-focussed hypnotherapy – this psychologist led therapy has shown benefit in reducing abdominal pain and discomfort in clinical studies by reducing gut sensitivity. (5). It targets the gut-brain axis and visceral hypersensitivity that can develop in IBS. Meditation and yoga have also been proven to be useful in reducing IBS symptoms.


  • Psychological therapy/ mindfulness: stress and anxiety can make the gut more sensitive and may trigger IBS symptoms. Mindfulness training, stress management and cognitive behaviour therapy (managing unhelpful thoughts) may reduce symptoms of IBS by reducing gut sensitivity.


  • Probiotics – Modification of the microbiome is an important part of IBS treatment.  The choice of probiotic will depend on your underlying symptoms, in which it can be broken down to IBS-M, IBS-D, and IBS-C.  The probiotics with the most evidence are:
  • IBS-M: : Align: longum infantis (OTC)
  • IBS-D : Bio-K: Acidophilus, L. caseiL. Rhamnosus (OTC)
  • IBS-C: Bio-Gaia: L. reuteri (OTC)


(12) Faecal transplant – is an area of intense research in IBS as well as many other conditions.  There are now at least 3 randomized control trials that demonstrate a significant reduction in symptoms in IBS patients.  In the most recent of these studies, a significant reduction of IBS symptoms was seen in 89.1% of patients. (4)  Faecal Transplant is offered as a treatment option at GastroX.

(12) Medicinal cannabis (Rx) – There are studies in IBS showing a reduction of symptoms and normalizing stool consistency with medical cannabis.  Dr Schneider are authorized to prescribe Medical Cannabis from the Therapeutic Goods Administration (TGA) and is actively involved in research in this area.

Finally, there are 2 medications designed specifically for patients with IBS that reduce abdominal pain and stool changes at the same time.

-IBS-D: Viberzi (Eluxadoline) (Rx) (6)

-IBS-C: Constella (Linaclotide) (Rx) (7)

Unfortunately, both of these medications are not available in Australia.  We have put in a request to have these medications made available in Australia.

In general, the best outcomes for treating IBS occur with an individualized and dynamic treatment plan that is developed by the patient and clinician together, and then is regularly monitored.’

OTC = over the counter

Rx = prescription medication