IBS symptoms and causes, explained


This chronic condition can be physically and emotionally draining. Here’s what you need to know.

By Annie Hayes

Constantly struggling with diarrhoea or constipation, bloating, and unexplained stomach pain? If your gut feels like it’s waging war against your intestines, and nothing helps to ease your swollen belly, you might be suffering from irritable bowel syndrome (IBS).

IBS is a chronic condition affecting the digestive system and it can be physically and emotionally draining. The good news? There are a number of simple lifestyle adjustments you can make to ease your discomfort and alleviate your symptoms.

We spoke to Dr Kevin Barrett, chair of the Primary Care Society for Gastroenterology, and Peter Thatcher, consultant gastroenterologist at the Royal Cornwall Hospital, about the causes, symptoms and treatment options for IBS:

What is irritable bowel syndrome?

IBS is characterised by a cluster of abdominal symptoms that typically occur all at the same time, including abdominal pain with either diarrhoeaconstipation or a combination of the two. There’s no specific cause and no single effective treatment for IBS. However, diet, stress, poor sleep and changes in gut bacteria are common triggers.

Symptoms vary in severity and duration from person to person. They’re not always persistent, and may ease and worsen repeatedly over time. IBS is the most common condition seen by gastroenterologists, and is more common in women than men. Some estimates suggest that as many as one in five adults in the UK have IBS at any one time.

Diet, stress, poor sleep and changes in gut bacteria are common IBS triggers.

Your bowel – or gut – extends from your stomach to your anus. It’s made up of the small intestine and the large intestine (colon), which process food from the stomach. Sometimes IBS is called irritable colon or spastic colon, but these names are misleading. IBS is not limited to the colon, and should be thought of as a multi-system disorder.

Your small intestine absorbs nutrients from food and passes undigested food into the large intestine, where the waste product is processed into faeces. Food is ushered through the intestines by muscular contractions known as peristaltic waves, which are controlled by communications between your brain and bowel. IBS occurs when these muscular contractions fail to coordinate.

IBS symptoms

A digestive system disorder can affect the gut anywhere from the mouth to the anus, which accounts for the diversity of symptoms seen in IBS. They can start at any age, but are most common in late teenage years or early adulthood.

Although IBS can be a distressing condition, it doesn’t increase your risk of bowel cancer, and very rarely causes bowel damage. The most common IBS symptoms include:

️ Pain and cramping

Abdominal pain is often the most prominent IBS symptom. One common cause relates to stretch receptors in your gut – the web of nerve endings that line it – which are activated at lower levels than in people without IBS, Dr Barrett explains. ‘This may be caused by the fermentation of non-digestible starches and other substances in the bowel, and the accumulation of gas and fluids,’ he says.

️ Bloating and gas

Cramping and bloating often go hand-in-hand. ‘The nerves in the bowel can get confused and start uncoordinated muscle spasm, leading to cramps,’ Dr Barrett says. ‘This can be triggered by an upset to the gut-brain communication and stress is a common trigger for this. Bloating can be a manifestation of both the excess gas and the abnormal muscle contractions.’

️ Diarrhoea

People with IBS may have diarrhoea, constipation, or sometimes a mixture of both. ‘The stools can be normal, but they can also pass small droppings or wet sloppy poos,’ says Dr Barrett. ‘Explosive bowel motions can also occur.’ When diarrhoea is a predominant symptom, it’s called diarrhoea-predominant IBS. Bowel movements are usually watery, loose and may contain mucus. The fear of experiencing a sudden, immediate urge to use the toilet can be a severe source of stress for people with this form of IBS.

️ Constipation

Constipation usually means you open your bowels fewer than three times per week. ‘Some people with IBS have a slow bowel transit and their poos can be large and hard to pass,’ says Dr Barrett. When the transit time is slow, your bowel absorbs more water from the food you eat, which affects your poop. People with constipation-predominant IBS often experience abdominal pain that eases when their bowels open. There’s also a sensation of the bowel movement being incomplete, which can be very frustrating.

️ Constipation and diarrhoea

IBS can affect how long it takes for food to move through your intestines. The speed at which it passes through your digestive system determines the amount of water in your poop, which can range from loose and watery to hard and dry. For some people with IBS, this can change on a regular basis, meaning they fluctuate between periods of constipation and diarrhoea. This type of IBS is often more severe, causing frequent and acute symptoms – particularly chronic abdominal pain, which is often relieved by using the toilet.

️ Food intolerance

Many people with IBS find that certain foods trigger their symptoms, such as wheat, dairy, beans, legumes, broccoli, garlic, onions, chocolate, processed foods and carbonated drinks. ‘If there is a clear trigger food that can be easily identified, then this may be omitted from the diet, but any more complicated food avoidance measures should ideally be carried out under the supervision of someone with appropriate training,’ says Dr Barrett.

Some people with IBS symptoms also experience:

  • Heartburn and indigestion
  • Headaches
  • Pain during sex (in women)
  • Passing urine more often
  • Fatigue and tiredness
  • Difficulty sleeping
  • Loss of appetite
  • Nausea
  • Anxiety
  • Depression

Symptoms of IBS usually occur during the day time, and rarely at night. If you experience night-time symptoms, you should see your GP. ‘Symptoms that occur overnight may be a sign of a serious underlying disease such as colorectal cancer or inflammatory bowel disease that can co-exist with IBS,’ says Dr Barrett. ‘If you are woken from your sleep by needing to open your bowels, please seek medical advice.’

IBS causes

We don’t know what causes IBS, but it seems a mix of psychological and physical factors are involved. About half of people with IBS date the start of their symptoms to a major life event, such as change of house, new job, or bereavement, which suggests that there’s a psychological trigger for IBS.

Up to 20 per cent of people date the start of their symptoms to a bout of acute gastroenteritis – an infection in the bowel that causes vomiting and diarrhoea. There’s evidence that people with IBS have increased gut sensitivity to external stimuli, such as stress – referred to as ‘increased visceral sensitivity’. Changes in gut microbes also appear to play a part.

If you suspect you have IBS, you should make an appointment with your doctor. The condition can mimic many other intestinal disorders, so it’s best to get checked out – especially if you experience any of the following symptoms:

  • Difficulty in swallowing when food gets stuck
  • Indigestion-type pain that wakes you up at night or persistent indigestion
  • Abdominal bloating that does not improve overnight
  • Significant and unexplained weight loss
  • Bleeding from the back passage
  • Chronic, painless diarrhoea

IBS diagnosis

There is no single blood testX-ray or scan that will diagnose IBS. The diagnosis is often made on the basis that typical symptoms are present, particularly in younger people who have had at least six months of change in bowel habit, abdominal pain and bloating. Blood tests may be taken to exclude other conditions such as coeliac disease, which can mimic IBS.

However, if you are more than 50 years old, additional investigations are performed to ensure the diagnosis is correct – especially if your symptoms include:

  • Unexplained weight loss
  • Abdominal or rectal masses (unexplained lumps)
  • Rectal bleeding
  • Anaemia
  • A family history of bowel or ovarian cancer
  • Being aged over 60 with a change in bowel habit lasting more than six weeks

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