IBS and Non-GI Functional Disorders

“Unexplained” Symptoms and “Functional” Disorders

People usually go to healthcare providers with symptoms, not with the names of diseases or conditions (diagnoses). The healthcare provider’s task is to make sense of the patient’s complaints within the framework of medical diagnoses and recognized diseases.

This is accomplished by a process of “history taking” (interview), physical examination, and diagnostic testing. The process is completed when the symptoms are resolved into the diagnosis of a specific disease, which is then treated with varying degrees of success.

Unfortunately, this idealization of the diagnostic process is often not realized in actual clinical practice. A significant percentage of patients who consult with healthcare providers in primary care or even specialist clinics have symptoms that remain unexplained after the diagnostic process is exhausted.

This is the case because modern medicine focuses on structural (often called “organic”) diseases, that is diseases that have a basis in the structure or anatomy of the body systems rather than functional disorders that have a basis in how the systems work.

Examples of structural abnormalities in the gastrointestinal tract are ulcer, inflammation, infection, and cancer.

Examples of functional abnormalities are disordered motility (where nerves or muscles in any portion of the digestive tract do not function with their normal strength and coordination) and hypersensitivity to pain (where persons sense or perceive pain or discomfort more easily, or at lower levels than is considered normal).

Most diagnostic tests (laboratory tests, radiology, endoscopy, and isotope scans) are designed to identify structural problems, but not disorders of function.

There are many examples of functional disorders in the gastrointestinal (GI) tract. The best-studied and most common of these are irritable bowel syndrome (IBS), and non-ulcer dyspepsia or functional dyspepsia.

As most patients with these disorders are aware, the results of diagnostic tests appear normal and the patient is often told that “nothing is wrong with them” or that “it’s all in their head.”

In effect, the symptoms remain “unexplained,” not because they cannot be explained but because some healthcare providers do not know how to explain them.

Functional Disorders in Various Body Systems

In the mid-19th century George Miller Beard, an American neurologist coined the term “neurasthenia” for a disorder that has also been known at times as Beard’s disease. He described patients with unexplained chronic fatigue and lassitude, which he referred to as nervous exhaustion. He reported that these patients had many additional signs and symptoms, including insomnia, back pain, nervousness, anxiety, depression, headache, difficulty in concentrating, reduced sexual impulse, abdominal pain, bloating and excess gas, diarrhea, and lack of appetite. Although he described patients of both sexes, he reported that neurasthenia had a female predominance.

This was an early description of a generalized functional disorder with associated psychological elements and evidence of somatization disorder (SD). These associations have gained recognition over the years for their potential contribution to the understanding and treatment of IBS.

Somatization disorder is a chronic condition with multiple physical complaints or symptoms and no recognizable physical abnormality. It is much more prevalent among women than men and usually begins at a young age (up to 30 years of age). Stress often worsens symptoms.

Learn more about stress and IBS

Source: IFFGD Publication #207, by Ami D. Sperber, MD.


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IFFGD is a nonprofit education and research organization. Our mission is to inform, assist, and support people affected by gastrointestinal disorders.

Our original content is authored specifically for IFFGD readers, in response to your questions and concerns.

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