Merck Manual

Please confirm that you are a health care professional

honeypot link

Functional Gastrointestinal Illness


Stephanie M. Moleski

, MD, Sidney Kimmel Medical College at Thomas Jefferson University

Last full review/revision Apr 2021| Content last modified Apr 2021
Click here for Patient Education

Often, no objectively measurable structural or physiologic abnormality for gastrointestinal complaints is found, even after extensive evaluation. Such patients are said to have functional illness, which accounts for 30 to 50% of referrals to gastroenterologists.

Functional illness may manifest with upper and/or lower gastrointestinal (GI) symptoms. (See also Irritable Bowel Syndrome and see the American College of Gastroenterology's monograph on management of irritable bowel syndrome.)

Functional GI disorders are disorders of the gut-brain interaction. Some evidence suggests that such patients have visceral hypersensitivity, a disturbance of nociception in which they experience discomfort caused by sensations (eg, luminal distention, peristalsis) that other people do not find distressing. Functional disorders are classified by symptoms related to a combination of not only visceral hypersensitivity but also motility disturbance, altered microbiota, mucosal and immune function, and central nervous system processing (1).

In some patients, psychologic conditions such as anxiety (with or without aerophagia), conversion disorder, somatic symptom disorder, or illness anxiety disorder (previously called hypochondriasis) are associated with GI symptoms. Psychologic theories hold that some functional symptoms may satisfy certain psychologic needs. For example, some patients with chronic illness derive secondary benefits from being sick. For such patients, successful treatment of symptoms may lead to development of other symptoms.

Many referring physicians and GI specialists find functional GI complaints difficult to understand and treat, and uncertainty may lead to frustration and judgmental attitudes. An effective physician–patient interaction reduces health care–seeking behavior by the patient. Physicians should acknowledge the patient's symptoms and provide empathy. Physicians should avoid ordering repeated studies or multiple drug trials for insistent patients with inexplicable complaints because this may promote symptom anxiety and health care–seeking behavior (2). When symptoms are not suggestive of serious illness, the physician should wait rather than embark on another diagnostic or therapeutic plan. In time, new information may direct evaluation and management. Functional complaints are sometimes present in patients with physiologic disease (eg, peptic ulcer, esophagitis); such symptoms may not remit even when a physiologic illness is addressed. In some patients, testing (eg, CT) may identify incidental abnormalities that are unrelated to the symptoms.

General references

  • 1. Drossman DA: Functional gastrointestinal disorders: History, pathophysiology, clinical features, and Rome IV. Gastroenterology 150:1262–1279, 2016. doi: 10.1053/j.gastro.2016.02.032

  • 2. Drossman DA: 2012 David Sun Lecture: Helping your patient by helping yourself: How to improve the patient-physician relationship by optimizing communication skills. Am J Gastroenterol 108:521–528, 2013. doi: 10.1038/ajg.2013.56

More Information

The following is an English-language resource that may be useful. Please note that THE MANUAL is not responsible for the content of this resource.

Click here for Patient Education
NOTE: This is the Professional Version. CONSUMERS: Click here for the Consumer Version


Professionals also read

Test your knowledge

A 32-year-old woman who is at 30 weeks’ gestation comes to the office because she has had pain on defecation during the past week. She says she also has had pain when attempting to cleanse the anal region as well as pain when sitting. Based on these findings, which of the following types of hemorrhoid is most likely to be noted on further evaluation of this patient?  
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID

Also of Interest