The term “diarrhea” originates from the Greek diarr, which means through, and rhein, which denotes flow. Although this descriptive term is appropriate for the symptoms, the word diarrhea may not have the same meaning for all patients and physicians. Diarrhea may denote an increase in the frequency, fluidity or volume of bowel contents, but there is no consensus on the interpretation of the term. To some, an increase in frequency without fluidity or increase in volume represents diarrhea, while for others a single component (e.g., increased frequency, or increased fluidity or volume without the other two components) does not represent this condition. To facilitate communication between physicians and patients, it is important that the history be elucidated in detail through a description of the frequency, volume and consistency of the bowel movements.
The causation also is important. Diarrhea may be caused by many different diseases, and, if possible, the cause of the diarrhea should always be determined in order that appropriate treatment may be given.
Another undefined question concerns the definition of when diarrhea becomes chronic. To provide an exact definition of chronicity is always difficult, not only for diarrhea but also for many other conditions. For instance, hepatologists still argue whether hepatitis becomes “chronic” at 3 months, 6 months or 1 year. The definition of chronicity, to some extent at least, depends also on the observer. The points of view of a family physician and a gastroenterologist may differ and the definitions by the treating physician and patient may also be quite different. While the physician may consider 2-week diarrhea still acute, the patient who goes to the bathroom 10 to 15 times a day may think that 2 weeks of this represents a very chronic disease indeed. Putting levity aside, however, most self-limiting episodes of diarrhea stop within days or a few weeks, and it is reasonable to define chronic diarrhea as a disorder that lasts for more than a month.
Dr. K.N. Jeejeebhoy, in his paper on the definition and mechanisms of diarrhea, discusses the pathophysiology of diarrheas of various origins, such as those caused by solute malabsorption, secretion or motility disturbances. Dr. W.C. Watson describes a most useful clinical approach to the elucidation of the causation of diarrhea. He stresses the diagnostic importance of a carefully taken history, with emphasis on the duration of the diarrhea, the presence or absence of abdominal pain, tenesmus, laxative use, previous surgery and the presence in the stool of blood or mucus (or both). He emphasizes the help that a thorough physical examination can provide. In the paper on investigation of chronic diarrhea, Dr. A. Groll describes the diagnostic modalities, including sigmoidoscopy, barium enema and radiography of the small bowel, and discusses the value of bacteriologic and histopathologic investigations. He details methods of investigation of the absorptive function of the small bowel, and the place and relative importance of these methods in the investigative process.
These papers present the approach and methodology of diagnosis. However, even with the current sophisticated methods, a definite etiologic diagnosis cannot always be made. When this happens physicians often diagnose the patient’s condition as nervous diarrhea (irritable bowel syndrome). Although in many cases this diagnosis may be correct, in patients with chronic diarrhea this assessment should be reviewed periodically. We should always remember that in nervous patients malignant conditions may develop over a period of time. In addition, our inability to establish an etiologic diagnosis for diarrhea may reflect only the fact that all questions have not yet been answered and that further research is needed.
As a result of developments in medicine the cause of diarrhea has been discovered for many patients in whom the original diagnosis was irritable bowel syndrome, allowing appropriate therapy to be instituted. For instance, before the hormonal causes of diarrhea were discovered, patients with Zollinger-Ellison syndrome or with the pancreatic cholera syndrome were often considered to be suffering from “nervous diarrhea“. The understanding of disaccharide digestion removed the stigma of irritable bowel syndrome from many patients with lactase deficiency. Before the use of peroral small-bowel biopsy, patients with adult celiac disease were often considered to have had nervous diarrhea. No doubt, after a number of unsuccessful diagnostic and therapeutic maneuvers, patients suffering from any of these organic diseases became sufficiently anxious to justify the physician’s labelling them with the diagnosis of irritable bowel syndrome or anxiety neurosis, or both. Their anxiety may have become quite severe, if for no other reason than that their first need on any social occasion or travel was to find the location of the nearest toilet.
The treatment of diarrhea, if possible, should depend on the underlying cause. It makes no more sense to treat a patient with ulcerative colitis for bacillary dysentery than to treat a patient with irritable bowel with a gluten-free diet for celiac disease. Dr. N. E. Diamant provides an excellent description of the irritable bowel syndrome and its treatment, Dr. J.L. Loudon discusses postoperative diarrheas and Dr. L.A. Edwards describes the treatment of the common infectious diarrheas. The topics were selected without prejudice and it is not suggested that there are no other, or more important, causes of diarrhea — for instance, inflammatory bowel disease, malignant conditions and many other causes are mentioned only briefly. The pathophysiology and the treatment of diarrheas due to primarily nongastrointestinal diseases, such as hyperthyroidism, diabetes mellitus, adrenal insufficiency and others are not discussed though they should always be considered as a possible cause of diarrhea.