19th July 2023

Functional Bowel Disorders (FBDs)

Definition and Pathophysiology 

FBDs are a group of conditions characterised by chronic GI tract symptoms for which no pathology can be found by conventional testing means. While previously defined as “lacking organic cause”, research has now demonstrated a correlation with abnormal gut-brain communications. This occurs secondary to abnormalities in GI motility, visceral hypersensitivity, altered mucosal and immune function, altered gut microbiota, and altered CNS processing. Risk factors include female gender, adolescents/young adults, and concomitant chronic psychiatric conditions (e.g., anxiety, depression, OCD), chronic pain syndromes (e.g., fibromyalgia) or functional conditions (e.g., chronic fatigue syndrome). They are the most commonly encountered GI pathologies in both primary and secondary care, therefore, it is important to recognise, diagnose and treat early.

Classification

The most common and well-known functional bowel disorder is Irritable Bowel Syndrome (IBS), estimated to affect 10-20% of the UK population. However, there are other FBDs which are defined according to the Rome IV criteria, shown in table 5.

Table 5: The Rome IV Diagnostic Criteria of FBDs

Assessment 

To formally diagnose an FBD, an organic cause for the patient’s symptoms must be excluded. A thorough history should exclude any red flag symptoms (such as GI bleeding, anaemia, unintentional weight loss) whilst also assessing lifestyle factors (diet, exercise, stress levels) and psychological state. Blood and stool testing is often required before attributing the patient’s symptoms to an FBD and managing them as such accordingly.

Management 

FBDs should be managed with a biopsychosocial approach involving a multidisciplinary team to deliver holistic care that is patient-specific with the aim of ameliorating symptoms and improving quality of life. Patients should be informed of an FBD diagnosis early with a thorough explanation that FBDs are chronic, often relapsing conditions and are, therefore, incurable and hard to treat. Management strategies, therefore, do not have curative intent and instead focus on improving symptom control and reducing their impact on the sufferer’s daily life, as shown in table 6.

Table 6: Management of FBDs