What Is Functional Diarrhea?

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Functional diarrhea is a health condition in which a person experiences chronic diarrhea without any clear-cut cause. Functional diarrhea is classified as a functional gastrointestinal disorder (FGD), as it is a health problem that reflects a problem with the way that the digestive system is functioning, but no sign of a disease process, injury, or structural problems shows up during diagnostic testing.

Symptoms of Functional Diarrhea

The main symptom of functional diarrhea is the experience of loose or watery stools, occurring without pain, in at least 75% of bowel movements. According to the Rome III diagnostic criteria for FGDs, this change in stool appearance must have occurred over at least a three-month period with onset at least six months prior to diagnosis.

How Functional Diarrhea Differs from IBS

Irritable bowel syndrome (IBS) is also an FGD. When chronic diarrhea is the predominant bowel problem in IBS, diarrhea-predominant irritable bowel syndrome (IBS-D) is diagnosed. Functional diarrhea differs from IBS-D primarily due to its lack of abdominal pain as a symptom. Both disorders may involve such symptoms as urgency, gas and bloating, mucus in the stool, and feelings of incomplete evacuation. It may be that functional diarrhea represents a subtype of IBS-D.

The Diagnostic Process

Functional diarrhea is diagnosed through a process of exclusion.

This means that it is offered as an explanation for ongoing symptoms only after other digestive disorders or health problems have been ruled out.

Typically your doctor will do a physical examination and take your health history. This may include a comprehensive review of your medication as many medications can cause diarrhea as an unwanted side effect.

Your doctor may also recommend blood work and a stool sample analysis. Other possible tests include a colonoscopy and/or endoscopy.

Your doctor may also ask about your diet. Chronic diarrhea can be a sign of:

Some people experience functional diarrhea after having had their gallbladders removed.

If other disorders have been ruled out and you are not experiencing any unusual symptoms, such as rectal bleeding or weight loss, a diagnosis of functional diarrhea may be made.

Treatment of Functional Diarrhea

The treatment of functional diarrhea has not gotten much attention separate from the focus on the treatment of IBS. Typically treatment is aimed at reducing its symptoms through dietary modifications, such as eliminating possible trigger foods and slowly increasing fiber intake. If stress appears to be a possible contributing factor, stress management activities might be helpful.

If your doctor believes that medication may be helpful, they might choose one or more of the following:


Dellon, E. & Ringel, Y. "Treatment of functional diarrhea." Current Treatment Options in Gastroenterology 2006 9:331-342.

"Rome III Diagnostic Criteria For Functional Gastrointestinal Disorders"