Diarrhea can be due to a number of infectious and noninfectious causes, including persistent intestinal infections, inflammatory enteropathies, and neoplastic disorders.
Travel-associated infections can include giardiasis, cryptosporidiosis, amebiasis, isoporiasis, strongyloidiasis, and schistosomiasis. Other infectious causes of diarrhea include tuberculosis, tropical sprue, human immunodeficiency virus (HIV), and Tropheryma whippelii.
Noninfectious causes include inflammatory bowel disease, adult-onset celiac disease, and neoplastic disorders such as intestinal lymphoma, villous adenoma, and functional neuroendocrine tumors including gastrinoma, carcinoid, and pancreatic endocrine tumors.
New England Journal of Medicine - Vol. 359, No. 1, July 3, 2008