IBS is probably the commonest disorder diagnosed in a gastroenterology outpatient setting. It's defined as more than six months of variable abdominal discomfort, often with bloating and a change in your bowel habits.

GPs use the Rome III criteria to diagnose IBS as “…recurrent abdominal pain or discomfort (including bloating) and a marked change in bowel habit for at least six months, with symptoms experienced on at least three days of at least three months.”

Two or more of the following must apply:

• Pain is relieved by a bowel movement
• Onset of pain is related to a change in frequency of stool
• Onset of pain is related to a change in the appearance of stool

You may find your symptoms get worse:

• During times of stress and major life events
• After eating certain foods - this can vary by individual
• When you're taking certain antibiotics
• Female sufferers may notice worsening symptoms with menstrual cycle

IBS can cause other symptoms too. These include:

• Feeling very tired
• Indigestion
• Low back discomfort
• Trouble sleeping
• Regular headaches
• Problems with your bladder, such as needing to pass urine more often and urgently, particularly at night
• Painful sex

The answer is we don’t know! Some individuals develop IBS after an episode of food poisoning or infective diarrhoea (eg Campylobacter) suggesting that a change in the gut bacteria (microbiome) may be important. In others, certain food items, such as wheat, dairy, or sugars, may worsen symptoms.

In others stress, anxiety, or worry may worsen IBS suggesting that the nerve endings in the gut are involved - the so-called Brain-Gut Axis, according to Dr Adam Harris, one of our Consultant Gastroenterologists. These patients may respond to treatment with drugs that alter their serotonin levels.

IBS is usually diagnosed according to strict national and international guidelines; it’s not a diagnosis of exclusion. Firstly, according to Dr Harris, “It's absolutely mandatory that a thorough history is taken to check that the patient's symptoms fit with the diagnosis. Symptoms suggestive of an inflammatory process or a strong family history of bowel cancer need to be considered carefully.”

Following a physical examination, a blood test is required to check for anaemia (thin blood), inflammation or coeliac disease. In individuals with diarrhoea, a stool specimen to measure calprotectin is required. This result must be negative to support a diagnosis of IBS; if raised further investigations, such as a colonoscopy will be needed.

Many studies have found that changing your diet, lifestyle or behaviour can be very effective at managing IBS symptoms. This includes:

• Taking a probiotic
• Changing to a low FODMAP (Fermentable Oligosaccharide Disaccharide Monosaccharide and Polyol) with supervision from a trained Dietician

Working out which parts of your diet trigger your IBS is important, as this differs depending on the individual. Typical IBS trigger foods include (but are not limited to):

• Dairy products
• Gluten
• Onions, garlic and tomatoes

Learning how to manage stress is also a key part of your recovery from IBS and this comes hand-in-hand with good lifestyle habits such as proper sleep (ideally eight hours per night) and regular moderate exercise.