Irritable bowel syndrome is a disorder characterized by chronic abdominal pain and altered bowel habits in the absence of an identifiable organic cause. Abdominal conditions occurring in the absence of identifiable causes are referred to as "functional" disorders. Irritable bowel syndrome is very common, affecting 10-15% of the population in first world countries. Many factors are thought to contribute to the development of IBS, but the exact mechanism has not been determined.

Symptoms

• Abdominal pain – Typically cramping in nature and varies in intensity. It may be associated with change in stool consistency, eating, emotional stress and even the menstrual cycle in females. It is usually relieved by passing stools.
• Changes in bowel habits – This may include diarrhoea, constipation or alternating diarrhoea and constipation.
• Bloating, flatus and belching.

Diagnosis

Because IBS occurs in the absence of organic disease, it is often first necessary to exclude other medical conditions before making the diagnosis. This may include blood tests, endoscopy (gastroscopy, colonoscopy) or radiology, depending on the presenting symptoms. A set of diagnostic criteria for various functional disorders has been created, and the most current version is called the Rome IV criteria.

Rome IV diagnostic criteria

According to the Rome IV criteria, the diagnosis of irritable bowel syndrome requires the following:

• Recurrent abdominal pain, on average 1 day per week for the past 3 months

AND

At least two of the following:

• Related to defecation
• Associated with a change in stool frequoency
• Associated with a change in stool consistency

AND

• Above criteria fulfilled for the past three months, with symptom onset at least six months ago