Functional Gastrointestinal (GI) Disorders

Functional GI disorders are common and for some people quite disabling and these people often don’t appreciate being told after going through a battery of tests that it is nothing serious.

The last resort diagnosis is a functional GI disorder when all investigations have failed. But have gastroenterologists given up too early? Functional disorder is often a catchall when it is not possible to make a diagnosis.

The patient has symptoms and a range of tests are performed. They all seem normal so it is called a functional disorder. Common functional disorder diagnoses include:

• Non-obstructive dysphagia.
• Non-cardiac chest pain.
• Functional heartburn.
• Non-ulcer or functional dyspepsia.
• Irritable bowel syndrome (IBS).
• Functional idiopathic constipation
• Functional diarrhoea.

Functional disorders have similar demographics in that they tend to be more common in females, occur most commonly in young to middle-age and they can be associated with musculoskeletal problems, genitourinary symptoms and a variety of so-called ‘all in the mind’ illnesses. This, as might be expected, confuses the diagnosis.
, and a variety of other psychosomatic problems,” said Prof Quigley.

The patient with a functional disorder often has multiple symptoms and may have comorbidity beyond the GI tract. There is a lot of overlap between the individual functional disorders and between non-GI symptoms. For example, half of those with IBS patients also have fibromyalgia and about half also have depression.

Some of those patients with a functional disorder have a cluster of symptoms. If bowel dysfunction is associated with abdominal pain it can be called IBS but if it is with constipation then it is called chronic constipation. It is difficult to know how to separate chronic constipation with IBS with constipation and occasional cramps and bloating.

Similarly these disorders may share certain pathologies such as motor abnormality or visceral hypersensitivity or autonomic dysfunction.

In some patients but not all their symptoms at presentation are affected by stress or psychological factors. Low grade infection or inflammation has been postulated as playing a role in some cases.

There are no distinctive biomarkers for these disorders. If you image the brain and stimulate pain in an IBS patient then you can see abnormal activity but it is not viable to image the brain of all IBS patients.
Diagnosis of a functional disorder is mainly by clinical exclusion using tests or by using the symptoms that are present or absent in a patient.

IBS in this way was usually in the past defined as abdominal pain or discomfort which is also associated with problem defecation or changes to frequency for a few months. This does not pick up all patients and definitely does not include those with bloating as a symptom. More recent definitions are more exclusive albeit even if more vague. The definition changed to abdominal discomfort associated with bowel habit changes, with discomfort including pain and bloating and a variety of other symptoms.

Even if patients fulfil the diagnosis of IBS then further investigations that are perhaps unwarranted are being performed.

IBS remains the most recognisable functional disorder. Many of the other conditions may be merely extensions of IBS. Only further research will delineate this.

The trigger for the spectrum of IBS conditions might be an interaction of multiple factors including the environment, infection, an individual’s psychological disposition, stressful life events or the presence of high anxiety or depression.


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