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Functional gastrointestinal disorders (FGIDs) can affect any part of the gastrointestinal (GI) tract, including the esophagus, stomach and intestines. They are disorders of function (how the GI tract works), not structural or biochemical abnormalities. As a result, x-rays, blood tests and endoscopies can show essentially normal results. FGIDs are also not psychiatric disorders, although stress and psychological difficulties can make FGID symptoms worse.
Approximately 25 million Americans have a functional GI disorder. FGIDs account for 40% of a gastroenterologist's practice. 50- 80% of persons with a functional GI disorder do not consult physicians, although they may take over-the-counter medications and report significantly higher rates of job or school absenteeism and disability.
The most common FGIDs are Irritable Bowel Syndrome (IBS) - which is altered bowel consistency combined with abdominal pain that is usually relieved with a bowel movement - and Functional Dyspepsia - ulcer-like symptoms with upper-GI pain and a feeling of indigestion or symptoms of milder discomfort with fullness and possibly nausea soon after eating.
There are three primary features of FGIDs - motility, sensation, and brain-gut dysfunction:
- Motility is the muscular activity of the GI tract. Normal motility (e.g., peristalsis) is an orderly sequence of muscular contractions from the top to the bottom. In FGIDs, the motility is abnormal - there can be muscular spasms that can cause pain, and the contractions can be very rapid (fast motility is diarrhea) or very slow (slow motility is constipation).
- Sensation is how the nerves of the GI tract respond to stimuli (for example, digesting a meal). In FGIDs, the nerves are sometimes so sensitive that even normal contractions can bring on pain or discomfort.
- Brain-gut dysfunction relates to the disharmony in the way the brain and GI system communicate. With FGIDs, the regulatory conduit between the brain and gut function may be impaired and this can lead to increased pain and bowel difficulties which can be worsened by stress.
Attention to FGIDs is increasing, as reflected in growing support for research in this area. The UNC Center for Functional GI & Motility Disorders is engaged in several research projects funded through the National Institutes of Health (NIH) and pharmaceutical companies. Research is focused on understanding mechanisms that may cause this group of disorders, treatment options to improve the symptoms, and understanding the complexity of symptoms. Publication of these research findings in peer-reviewed scientific journals helps to educate other physicians about this rapidly expanding field.
Current State of Knowledge about FGIDs
It is safe to assume from writings of physicians and historians that FGIDs have existed throughout history. But, the lack of identifiable cause prevented their classification as diseases and may have made their diagnosis and treatment "second class" in medical school, residency training, and research. There were only occasional reports of these disorders until the middle of the century, when systematic investigation began. Scientific attention to understanding and caring for patients with FGIDs developed only within the past 20 years and since then has grown steadily. Part of the reason for this growing interest relates to the symptoms being viewed as a syndrome with treatment options, as well as the use of new investigative techniques in GI physiology.
Additional research is still needed with regard to the pathophysiology, classification and treatment of FGIDs, given their health care impact. But, research on the psychosocial aspects of FGIDs has led to three general observations:
- Psychological stress exacerbates GI symptoms -- The evolving theory suggests that chronic GI symptoms are generated by a combination of intestinal motor, sensory and central nervous system (CNS) activity. The mechanism for these associations relates to the existence of bi-directional pathways between the central and enteric nervous systems, the so-called "brain-gut" axis. These bi-directional pathways provide the linkage between sensation in the gut and intestinal motor function. External stressors and cognitive information (emotion, thought) have, by virtue of their neural connections to the brain, the capability to affect GI sensation, motility and secretion. Conversely, not only does the brain affect the gut, but activity in the gut affects central pain perception, mood and behavior.
- Psychosocial disturbances amplify illness experience and adversely affect health status -- Patients with FGIDs can show greater psychological difficulties than healthy research subjects or other medical patients. For example, research has shown that persons with IBS who do not consult a physician are psychologically similar to healthy (non-IBS) study subjects. This shows that IBS is not a psychiatric disorder; instead, it shows that psychosocial factors affect the individual's illness experience/perception and health outcomes, including physician consultation practices.
- Having a functional GI disorder impairs quality of life -- Any chronic illness, including IBS, will affect a person's health-related quality of life (i.e., one's general well-being, ability to carry out day-to-day activities, concerns about the illness, satisfaction with health care). The investigation of clinical and psychosocial outcomes - including quality of life - is still relatively new in the field of gastroenterology.