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. Unfortunately, it is often undertreated with many patients continuing to experience long-term problems.

What causes Irritable Bowel Syndrome?

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).
  2. 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) (3). 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).
  3. 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.

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.

The main symptoms of IBS are:
(i) abdominal pain
(ii) bloating
(iii) changes in bowel habit (either diarrhoea or constipation)

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.

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

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:

(i) 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.

(ii) 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).

(iii) Fiber and laxatives – a bulk-forming soluble fiber such as psyllium seed (Metamucil – OTC) can help both diarrhoea and constipation. Laxatives such as PEG 3350 (Movicol or Osmolax) (OTC), Lactulose (OTC), Coloxyl with senna (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.

(iv) Anti-diarrhoea medictions – including Loperamide (OTC) and Lomotil (Rx)

(v) Anti-spasmodics – for the treatment of abdominal cramping: Iberogast (OTC), Peppermint Oil (OTC), Mebeverine (Colofac) (Rx), Amitriptyline (Endep) (Rx) and Hyoscine (Buscopan) (Rx) can be helpful.

(vi) Gut-focussed hypnotherapy – this psychologist led therapy has shown benefit in reducing abdominal pain and discomfort in clinical studies (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.

(vii) 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. casei, L. Rhamnosus (OTC)
  • IBS-C: Bio-Gaia: L. reuteri (OTC)

(viii) Herbal supplements – there are several on the market including Phloe (kiwifruit extract – OTC).

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

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 currently 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

  • Guarner F, Malagelada JR Gut flora in health and disease. 2003 Feb 8; 361(9356):512-9.
  • ACG Clinical Guideline: Small Intestinal Bacterial OvergrowthPimentel, Mark MD, FRCP(C), FACG; Saad, Richard J. MD, FACG; Long, Millie D. MD, MPH, FACG (GRADE Methodologist); Rao, Satish S. C. MD, PhD, FRCP, FACG The American Journal of Gastroenterology: February 2020 – Volume 115 – Issue 2 – p 165-178
  • Martinucci IBlandizzi Cde Bortoli NBellini MAntonioli LTuccori MFornai MMarchi SColucci R. Genetics and pharmacogenetics of aminergic transmitter pathways in functional gastrointestinal disorders 2015;16(5):523-39. doi: 10.2217/pgs.15.12.
  • Efficacy of faecal microbiota transplantation for patients with irritable bowel syndrome in a randomised, double-blind, placebo-controlled study Magdy El-­Salhy ,1,2 Jan Gunnar Hatlebakk,2 Odd Helge Gilja,2 Anja Bråthen Kristoffersen,3 Trygve Hausken Gut Microbiota Dec 2019
  • Miller, H.R. Carruthers, J. Morris, S.S. Hasan, S. Archbold, P.J. Whorwel, Hypnotherapy for irritable bowel syndrome: an audit of one thousand adult patients. Alimentary Pharmacology and Therapeutics 4 March 2015
  • Anthony J. Lembo, M.D., Brian E. Lacy, M.D., Ph.D., Marc J. Zuckerman, M.D., Ron Schey, M.D., Leonard S. Dove, Ph.D., David A. Andrae, Ph.D., J. Michael Davenport, Ph.D., Gail McIntyre, Ph.D., Rocio Lopez, Ph.D., Lisa Turner, R.Ph., and Paul S. Covington, M.D. Eluxadoline for Irritable Bowel Syndrome with Diarrhea n engl j med 374;3 January 21, 2016
  • Randomised clinical trials: linaclotide phase 3 studies in IBS‐C – a prespecified further analysis based on European Medicines Agency‐specified endpoints M. M. Quigley, J. Tack, W. D. Chey, S. S. Rao, J. Fortea, M. Falques, C. Diaz, S. J. Shiff, M. G. Currie, J. M. Johnston 01 November 2012 Alimentary Pharmacology and Therapeutics