Diagnosing IBS

IBS is a condition characterised by abnormalities in the way the bowel functions. As such, there is no specific laboratory test for diagnosing it. Diagnosis relies on patients showing a persistent pattern of IBS symptoms (i.e., recurring abdominal discomfort, changes in bowel habits, e.g., diarrhoea, constipation), and conducting tests that eliminate the possibility of other gastrointestinal conditions (e.g., inflammatory bowel disease, coeliac disease, bowel cancer). Perspectives on the diagnosis of IBS have changed in recent times. In the past, diagnosing IBS often involved an extensive process of disease exclusion. Nowadays, doctors tend to only subject patients to some tests if there is a convincing reason to do so, such as the presence of ‘red flag’ symptoms that can indicate the condition is not IBS. These include signs such as

• Rectal bleeding
• Fever
• Unintentional weight loss
• Abnormal blood tests
• Anaemia
• Symptoms that ‘change’ (e.g., change in the location, severity of pain)
• Family history of gastrointestinal diseases such as inflammatory bowel disease (e.g., Crohn’s disease, ulcerative colitis, bowel cancer, coeliac disease).

There are several testing methods used to diagnose IBS. The tests used to diagnose IBS will depend on the presenting signs and symptoms, as well as patient characteristics (e.g., age). Diagnosis begins with your doctor assessing your symptoms for characteristics of IBS, such as

• Abdominal pain related to bowel movements
• Pain that improves/worsens with bowel movements
• Increased/decreased frequency of bowel motions

Your doctor will also likely ask about

• When you first started noticing symptoms
• Duration/frequency of symptoms
• Family history of gastrointestinal diseases