Treatment of functional diarrhea.

Functional diarrhea (FD), one of the functional gastrointestinal disorders, is characterized by chronic or recurrent diarrhea not explained by structural or biochemical abnormalities. The treatment of FD is intimately associated with establishing the correct diagnosis. First, FD needs to be distinguished from diarrhea-predominant irritable bowel syndrome (IBS), in which, unlike in FD, abdominal pain is a primary diagnostic criterion. Next, FD must be differentiated from the myriad organic causes of chronic diarrhea. Unlike IBS, in which a positive diagnosis can be made with an acceptable level of confidence using symptom-based criteria and minimal testing, the diagnosis of FD is still primarily a diagnosis of exclusion. Thus, the onus is on the physician to eliminate potential underlying causes, both common and uncommon, in the proper clinical setting. Once the diagnosis has been established, the clinician and patient should first focus on identifying, eliminating, and/or treating aggravating factors. These may include physiologic factors (eg, small bowel bacterial overgrowth), psychological factors (eg, stress and anxiety), and dietary factors (eg, carbohydrate malabsorption). Thereafter, appropriate treatment for functional diarrhea may be instituted. Treatment options include dietary and lifestyle modification, pharmacologic therapies, and alternative modalities. Although many of these strategies have been studied in IBS, almost none of them has been examined specifically in FD. Furthermore, given the poorly understood pathophysiologic basis of FD, these treatments primarily target a patient's symptoms and presumed altered physiology rather than underlying etiologic mechanisms. Therefore, we stress that treatment must be approached in an individualized manner and that dietary and pharmacologic therapies should be part of a comprehensive therapeutic approach in which education and reassurance form the foundation. In general, we attempt to remove dietary triggers and recommend increased fiber intake. We then add anticholinergic, antispasmodic, antimotility, and antidiarrheal agents as the first line of pharmacotherapy. Should a patient not respond to these, and for patients who have a significant degree of psychological dysfunction, central acting agents, including antidepressants and/or anxiolytics, may be beneficial. During the treatment period, we also recommend that physicians keep an open mind. If signs or symptoms that suggest an ongoing or previously unrecognized organic process develop, then a re-evaluation of the clinical picture is indicated.