Medical diagnosis generally requires observed anatomical or physiological abnormalities. Description of the illness and criteria for its diagnosis follow naturally. Recognized symptoms can then be attributed to the observation, and a diagnosis predictably follows. In the case of the functional disorders, such a process is impossible. As there are no observed defects, we only know of the existence of these disorders through the words of our patients. Hence there can be no animal model. Parrots may talk, but are not likely to discuss their bowels. The need to define these disorders of unknown pathology represents a major paradigm shift, a substantial change in thinking for doctors whose training concentrates on basic science and palpable evidence. As more than half of the gut disorders encountered by gastroenterologists and primary care doctors are functional, we must face the reality that scientific evidence to explain these disorders does not exist, and develop alternative methods to identify disease.

For too long, functional diseases have been described by what they are not, rather than as real entities. Yet they are real enough to our patients. Not only does this exclusive approach fail to provide the patient with the dignity of a diagnosis, but it also generates needless tests and consultations. The fruitless pursuit of an anatomical cause renders functional disorders diagnoses of exclusion. Their very numbers and cost demand a more positive approach.

There are many references to gut dysfunction in the ancient and early European literature. However, the first credible English language descriptions of irritable bowel syndrome (IBS) appeared in the early 19th century. One such description of the IBS in 1818 drew attention to the three cardinal symptoms of IBS; abdominal pain, “derangement of. . .digestion” and “flatulence.”1 A few years later, Howship described a “spasmodic stricture” of the colon reflecting the …