Irritable bowel syndrome (IBS)

About one in five people experiences the symptoms of irritable bowel syndrome (IBS) at some point in their lives. IBS is commonly described as a functional gastrointestinal disorder. A newer way of describing it is as a disorder of brain–gut interaction, which highlights how closely the brain and gut function are linked.

More women than men are affected, and symptoms tend to appear first in early adulthood. There is no single cause for IBS. Each person experiences symptoms because of their own mix of factors, which can include changes of routine, emotional or psychological distress, infection, unhelpful toileting habits and diet. Other contributing factors include neurotransmitters, the gut microbiota and the way the bowel muscles move (intestinal motility).

Importantly, IBS does not cause lasting damage and does not lead to serious bowel conditions such as cancer or inflammatory bowel disease.

Symptoms of IBS#

Common signs of IBS include:

• Abdominal pain or cramping that is often relieved by passing wind or a bowel motion
• Diarrhea and constipation, which may occur together
• A feeling that the bowels are not fully emptied after passing a motion
• Abdominal bloating and distension

None of these symptoms are unique to IBS. It is uncommon for IBS to cause these symptoms for the first time after the age of 40, so new symptoms later in life should always be checked.

Main categories of IBS#

IBS can be divided into three broad patterns:

• Constipation-predominant – the person tends to alternate constipation with normal stools.
• Diarrhea-predominant – the person tends to have loose stools, which may be frequent. The need to use the toilet can be urgent and hard to delay. Incontinence may sometimes be a problem.
• Alternating – constipation and diarrhea occur in turn.

Causes and triggers#

The underlying cause is likely to involve several factors that are different for each person. Some factors are known to trigger flare-ups in susceptible people, including:

• Infection – an episode of gastroenteritis can leave ongoing bowel symptoms long after the bacteria or virus has cleared.
• Food intolerance – foods that are poorly absorbed, such as the carbohydrate “sugars” lactose, fructose and sorbitol, can affect the nerves of the bowel in susceptible people.
• Emotional stress – strong emotions such as anxiety or stress.
• Medication – certain types, such as antibiotics, antacids and painkillers, can lead to constipation or diarrhea.

In some people the signalling between the brain and the gut is poorly regulated, leading to a more sensitive gut. This is sometimes called “visceral hypersensitivity”.

Getting a diagnosis#

If you think you may have IBS, it is important to seek medical advice so that other conditions can be ruled out. These include diverticulitis, inflammatory bowel disease, celiac disease (an immune intolerance to gluten, found in wheat and other grains) and lactose intolerance, which can cause bloating, cramps and diarrhea.

Most people can be diagnosed without invasive testing. Assessment may involve:

• A full medical check-up
• Blood tests, including tests for celiac disease
• Stool tests to help exclude inflammatory bowel disease
• In some cases, examination of the stomach or bowel under sedation (gastroscopy or colonoscopy)

Treatment for IBS#

IBS can be managed well with treatments tailored to the individual. Clinicians often start by helping you identify and avoid your own triggers. Options may include:

• Moderating common gas-producing foods, or following a structured diet such as a low-FODMAP diet (reducing fructose, lactose and sorbitol) with a trained dietitian
• An increase in dietary fibre, together with plenty of clear fluids
• Antispasmodic medicines that ease cramping, such as mebeverine, and peppermint oil capsules
• Antidiarrhoeal medicine, such as loperamide, for diarrhea-predominant IBS
• Laxatives for constipation
• Tricyclic antidepressants, which can help with pain and bowel frequency in IBS

Using an antidepressant does not mean that IBS is caused by depression or anxiety; these medicines act on the gut and the nerve pathways involved.

Psychological therapies, including cognitive behavioural therapy and gut-directed hypnotherapy, can also be effective. These involve a trained psychologist and may be delivered in person or through online programs.

Behavioural and pelvic floor therapies#

Sometimes IBS symptoms are caused by difficulty emptying the bowel effectively. Trained pelvic floor physiotherapists can treat this well.

A small number of medicines that act on the interaction between serotonin and the nerve cells of the colon have been developed and shown to help selected groups in clinical trials. These include alosetron, cilansetron and tegaserod. Safety concerns have led to some of these being withdrawn or restricted, and they are not widely available. Microbiota-altering therapies such as faecal microbiota transplantation are still considered experimental, and early studies have not shown them to be clearly effective.

People with IBS can become frustrated and feel their symptoms are not taken seriously. This frustration, along with poorly matched therapy, can make symptoms worse. Finding a health professional experienced in treating IBS is important, and being cared for by a multidisciplinary team is ideal.

Key points#

• About one in five people experiences the symptoms of irritable bowel syndrome (IBS) at some time.
• IBS is commonly described as a functional gastrointestinal disorder, and more recently as a disorder of brain–gut interaction.
• More women than men are affected, and symptoms tend to first appear in early adulthood.
• There is no single cause for IBS; each person experiences symptoms because of their own mix of factors.
• IBS can be managed well with treatments tailored to the individual.

Where to get help#