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.
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:
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)
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.
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.
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
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.
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).
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).
(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.
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.
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:
(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