Heinz F. Hammer, MD Guest Editor

Chronic diarrhea may result in a multitude of clinical and social problems for patients. In a small minority of patients chronic diarrhea is the main symptom and can be life threatening, due to excessive fluid and electrolyte losses, for example, in some endocrine tumors. In a considerably larger proportion of patients chronic diarrhea is part of a symptom complex, like in inflammatory bowel diseases, and in these patients other symptoms, like blood loss or abdominal pain, may have more clinical relevance than diarrhea. However, the most frequent causes of diarrhea are functional and have neither life-threatening consequences nor are they a sign of a severe underlying disease, although also in these patients chronic diarrhea may severely inflict on quality of life, due to the interference of diarrhea, fecal urgency, or fecal incontinence with normal professional or social daily activities.

The topics selected for this issue of Gastroenterology Clinics of North America reach beyond knowledge that can be easily obtained from the standard gastroenterology textbooks. They rather focus on specific topics and present in-depth reviews on specific issues in the diagnostic evaluation and pathophysiology of chronic diarrheal disorders. The issue starts with an article on the practical value of stool analysis in detecting the etiology of idiopathic chronic diarrhea. The authors of this article have complemented their large experience by recent research. This is followed by an article that thoroughly describes normal colorectal histology and, based on this knowledge, extends to histopathologic findings in patients with chronic diarrhea. The recent interest in the role of the bacterial flora as a cause or treatment of chronic diarrhea is discussed in the third article. This is followed by an article summarizing the role of circulating agents in the pathogenesis of diarrhea and by articles on some specific conditions or disorders causing diarrhea, that is, diarrhea in carbohydrate malabsorption, functional diarrhea, celiac disease, inflammatory bowel diseases, and diarrhea in the immunocompromised host.

I am confident that this issue offers the most current information regarding this important condition and I am grateful to the authors that they have focused on information that can be taken to the bedside and immediately applied.