When the digestive system is not functioning normally but no structural causes are found, the problem might be a functional bowel disorder.1 One definition of a functional bowel disorder is below. Put simply, these disorders are problems related to gut-brain interaction.1
Definition from the International Foundation for Functional Gastrointestinal Disorders:
“The term ‘functional’ is generally applied to disorders where the body’s normal activities in terms of the movement of the intestines, the sensitivity of the nerves of the intestines, or the way in which the brain controls some of these functions is impaired. However, there are no structural abnormalities that can be seen by endoscopy, x-ray, or blood tests. Thus it is identified by the characteristics of the symptoms and infrequently, when needed, limited tests.”
The diagnosis of a functional bowel disorder is based on symptoms that have been going on for at least 6 months and are present at least 3 days per month for the last 3 months.2 The specific symptoms depend which part of the digestive tract is affected. Symptoms may include pain, bloating, irregular bowel movements, diarrhea,or constipation.2
About 25% of people in the United States have a functional bowel disorder.1 These disorders are among the most common digestive problems.
Types of Functional Bowel Disorders
Irritable bowel syndrome is a common functional bowel disorder that affects the middle and lower digestive tract.1 Functional disorders can also affect other areas of the digestive tract:1
Esophageal disorders affect the esophagus (food pipe). These include functional chest pain, functional heartburn, difficulty swallowing, and the feeling of having a lump in the throat.
Gastroduodenal disorders affect the stomach and first part of the small intestine. These include functional upper abdominal pain, belching disorders, nausea and vomiting disorders, and problems with regurgitation.
Bowel disorders include irritable bowel syndrome, as well as functional constipation, functional diarrhea, and functional bloating.
Anorectal disorders cause problems with bowel movements that are not caused by a structural or nerve problem.
This list does not include all the functional bowel disorders.1 There are other disorders that affect infants, young children, and adolescents. Some functional bowel disorders are considered “centrally mediated,” which means that they cause abdominal pain that is not related to gut function.
Diagnosing Functional Bowel Disorders
Functional bowel disorders do not cause changes that can be measured with blood tests or seen with imaging tests.1 The diagnosis is based on symptoms. The symptoms of different functional bowel disorders often overlap and may change over time.3
If your health care provider suspects that you have a functional bowel disorder, she or he will probably ask you to describe the type, frequency, and duration of your symptoms. In many cases, your symptom history will be enough to make the diagnosis.3 If you have “alarm features” or “red flag symptoms,” you may need to have additional tests. These tests are needed to rule out other digestive diseases that could be causing your symptoms.
Quality of Life
Functional bowel disorders are not life threatening, do not damage the intestine, and do not lead to cancer.2 However, they certainly can affect daily life.4 Patients report that they have to limit their usual activities—such as missing work—due to their disorder. Many feel that they have lost “a great deal” of control over their lives and are dissatisfied with their treatment options.4
It can be frustrating to live with an “invisible” illness that causes a great deal of discomfort and inconvenience to you, but may be difficult for friends, family—and even your health care provider—to recognize. Additionally, functional bowel disorders are different for everyone, which makes it challenging to find treatments that work. You may be able to improve your quality of life by becoming an expert in your own disease, finding a health care provider with whom you can partner, and educating loved ones about your condition.
International Foundation for Functional Gastrointestinal Disorders. Functional GI Disorders. Accessed June 14, 2016 at: http://www.iffgd.org/gi-disorders/functional-gi-disorders.html
Häuser W, Layer P, Henningsen P, Kruis W. Functional bowel disorders in adults. Dtsch Arztebl Int. 2012;109:83-94.
Gunnarsson J, Simrén M. Efficient diagnosis of suspected functional bowel disorders. Nat Clin Pract Gastroenterol Hepatol. 2008;5:498-507.
IBS Patients: Their Illness Experience and Unmet Needs. IFFGD 2009.