Irritable Bowel Syndrome (IBS)

What is IBS?

Irritable Bowel Syndrome, also known as IBS, is one of the most common and debilitating gastrointestinal disorders that significantly affects the digestive system.
It is a group of symptoms which consistently occur together. The most common symptoms are stomach cramps, bloating, discomfort, diarrhoea and constipation which usually alternates with each other.
IBS can affect your everyday life.

What are the different types of IBS

Symptoms of IBS vary among people. As a functional Gastrointestinal (GI) disorder it comes in multiple forms.

IBS-C refers to IBS with constipation predominantly and it is one of the more common types.

IBS-D is also called IBS with diarrhoea.

IBS-M includes the mixed bowel habits i.e., alternating diarrhoea and constipation.

Post-Infectious IBS occurs after you have had a gut infection. Diarrhoea, vomiting are important signs.

Post-diverticulitis IBS. People are at risk of developing IBS after they have had diverticulitis.

What causes IBS?

The exact cause of IBS is unknown, but some factors appear to play a role in IBS:

  • Altered muscle contractions in the intestine: if the muscle contracts stronger and for a longer period, then it may cause diarrhoea. If the muscle contractions are weaker, it can cause constipation.
  • Sensitive nerves in the gastrointestinal tract; this can occur in response to gas or stool in the intestine causing the nerves to overreact. This may lead to discomfort and IBS symptoms.
  • As mentioned above, post-infections IBS (PI -IBS) can occur after a bout of gastroenteritis (or sometimes referred to as a tummy bug). Food poisoning is a common cause of a bacterial infection in the gut. Not everyone who experiences food poisoning or gastric infection will go on to PI-IBS but it increase the risk. Symptoms can still develop many years after the infection which can make it difficult to identify.
  • An imbalance of bacteria in the intestine called SIBO (Small intestinal bacterial overgrowth) results in an overgrowth of bacteria in the small intestine. Some studies have indicated that up to 80% of people with IBS have SIBO. Because of the prevalence of SIBO and the fact there is treatment available for it, we will discuss this in more detail below.

Small Intestinal Bacterial Overgrowth and IBS

To understand the relationship between SIBO and IBS, we first need to look at what SIBO means.

SIBO stands for Small Intestinal Bacterial Overgrowth. It refers to the condition where there is an abnormal increase in the bacterial population of the small intestine.

Most of our gut bacteria reside in the large intestine and performs a variety of important roles in the body. A much lower number of bacteria are located in the small intestine. If there is an abnormally high number of bacteria in the small intestine, it can interfere with digestion and absorption.

Briefly explaining, if the movement of food particles in the digestive tract slows down, it provides optimal conditions for bacteria to overgrow, resulting in a range of symptoms, for example, diarrhoea, abdominal bloating, and may even lead to malnutrition. So, those with SIBO suffer almost the same symptoms as the people with IBS do.

This overlap of symptoms makes it confusing  to reach a diagnosis. However, it is worth mentioning that the diagnosis and the management of SIBO can be quite straightforward, whereas IBS can only be diagnosed when all other possible diagnoses have been ruled out, meaning that IBS is a diagnosis of exclusion.

Undoubtedly, there are many other potential reasons for the development of irritable bowel syndrome, but further ongoing studies indicate that up to 80% of the people clinically diagnosed as IBS have SIBO too.

The SIBO Test

The Hydrogen and Methane breath test is used to detect Small Intestinal Bacterial Overgrowth (SIBO). This is a simple and non-invasive investigation.

The SIBO test can be done either in one of our clinic locations or the test can be perfomed at home using a home testing kit.

Samples are sent back to GastroLife for analysis.







How is the test done?

A baseline breath sample is measured by blowing into a sample collection bag. Following this, you will drink a sugar based testing solution. You will then b repeat the breath samples at regular intervals. Testing duration is typically between 2-3 hours.

How can breath samples tell me what is happening in my intestine?

If there is too much bacteria present in the small intestine, it will interfere with the normal digestion and absorption process. The overgrowth of bacteria ferment food, more often carbohydrates, in the small intestine. As a result, gases such as hydrogen and methane are produced. These gases are only produced by bacteria and not by any other part of the body. These gases have a small size and can pass easily through the wall of the intestine and into your blood circulation. When your blood travels around your body to your lungs, gas exchange takes place, and these gases are detected from exhaled breath samples.

Can SIBO be detected with a Gastroscopy (camera test)?

The camera that passes through your mouth only reaches the first part of the small intestine. If a bacterial overgrowth is present in the mid or distal part of the small intestine, it is unlikely to be detected. A sample of fluid from the upper part of the intestine can be taken with the camera however, the samples are often contaminated with oral and pharyngeal bacteria as the camera is withdrawn through the mouth. The sample would then have to be cultured in a lab which is quite expensive and not traditionally done in Ireland for SIBO. The breath test can detect bacteria all the way through the proximal, mid and distal small intestine.

Who performs the test in the clinic?

The test is performed and analysed by fully accredited Gastrointestinal Physiologists. Melissa is our senior Scientist and has over 14 years’ experience, (of which 10+ years were spent in St. James’s Hospital Dublin) specialising in GI function testing.