How can I differentiate between irritable bowel syndrome and other gastrointestinal disorders in a primary care setting?

To differentiate irritable bowel syndrome (IBS) from other gastrointestinal disorders in primary care, start with a detailed symptom assessment focusing on abdominal pain or discomfort that is either relieved by defaecation or associated with altered bowel frequency or stool form. IBS diagnosis requires abdominal pain or discomfort plus at least two of the following: altered stool passage (straining, urgency, incomplete evacuation), abdominal bloating or distension, symptoms worsened by eating, and passage of mucus.

Use the Bristol Stool Form Scale to help patients describe stool quality and quantity. This aids in characterising bowel habit changes typical of IBS.

Assess symptom duration, requiring symptoms to be present for at least 6 months.

Perform a clinical examination and assess for 'red flag' features that suggest other diagnoses, such as signs of cancer or inflammatory bowel disease. Presence of red flags warrants referral for further investigation.

Order basic blood tests to exclude other conditions: full blood count, inflammatory markers (ESR or CRP), and antibody testing for coeliac disease (endomysial antibodies or tissue transglutaminase).

Do not routinely perform invasive or extensive investigations (e.g., colonoscopy, faecal occult blood, hydrogen breath tests) if IBS diagnostic criteria are met and no red flags are present.

Consider other gastrointestinal disorders if symptoms do not fit the IBS pattern, red flags are present, or if initial management fails.