What Is a Functional Bowel Disorder?

When the digestive system is not functioning normally but no structural causes are found, the problem might be one of several functional bowel disorders. One definition of a functional bowel disorder is below. Put simply, these disorders are problems related to gut-brain interaction.¹

What is a functional bowel disorder?

Here is the definition from the International Foundation for Functional Gastrointestinal Disorders: “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."¹

The diagnosis of a functional bowel disorders depends on the specific disorder. In general, it is based on symptoms that started at least 6 months before and have been present at least once per week for the last 3 months. The specific symptoms depend which part of the digestive tract is affected. Symptoms may include pain, bloating, irregular bowel movements, diarrhea, or constipation.²

Experts estimate that at least one-quarter of people in the United States have a functional bowel disorder. These disorders are among the most common digestive problems.¹

IBS and other functional bowel disorders

Irritable bowel syndrome is a common functional bowel disorder that affects the middle and lower digestive tract. 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. 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.¹

Diagnosing functional bowel disorders

Functional bowel disorders do not cause changes that can be measured with blood tests or seen with imaging tests. The diagnosis is based on symptoms. The symptoms of different functional bowel disorders often overlap and may change over time.¹

If your doctor suspects that you have a functional bowel disorder, they 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. But you may need to have additional tests to rule out other digestive diseases that could be causing your symptoms.^1,2

Quality of life

Functional bowel disorders are not life threatening, do not damage the intestine, and do not lead to cancer. However, they certainly can affect daily life. Patients report that they have to limit their usual activities – such as miss 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.^2,3

It can be frustrating to live with an “invisible” illness that causes discomfort and inconvenience to you but may be difficult for others 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 good doctor to partner with, and educating loved ones about your condition.