Chronic Diarrhea is defined as diarrhea that persists for more than 4 weeks.  Causes There are many possible causes for chronic diarrhea: Infections do not generally cause this condition.  Medications– Medications may cause drug-induced diarrhea may without you realizing it. An example may be as simple as an antacid, which could lead to diarrhea if you are taking on a regular basis, as most of these contain magnesium.  Surgery – We may see this condition after certain surgeries are performed; in particular, a vagotomy or gastrectomy, cholecystectomy (gallbladder removal) or bowel resection.  Abdominal pelvic radiation therapy. Endocrine diseases, including hyperthyroidism, diabetes mellitus, hypoparathyroidism or Addison's disease.  Circulatory problems, such as congestive heart failure, vasculitis or poor bowel circulation.  Immune deficiency syndromes like AIDS or various neurologic diseases.  Chronic bacterial infections also can be a cause - the most common of these would be tuberculosis, or parasites like Giardia, Strongyloides, Yersinia.  Inflammatory bowel disease, such as Crohn's disease, ileitis, or ulcerative colitis. These conditions lead to chronic inflammation of the lining of the bowel wall, resulting in seepage of secretions, mucous, blood and hypermotility, all resulting in chronic diarrhea.  Occasionally diverticulitis of the colon or a collagenous colitis might also be a factor.  Tumors of the colon, especially those in the lower part of the colon. These could be either colon cancers or colon polyps, as well as abdominal lymphomas or carcinoid tumors. Glandular tumors like pancreatic carcinoma, gastrinoma, thyroid carcinoma or carcinoid tumors can also lead to diarrhea.  Maldigestion or malabsorption – This could be secondary to a decrease in production of digestive enzymes from either the pancreas or the bile, resulting in poor absorption and thus diarrhea. Additionally, certain conditions of the lining of the small intestine, which prevent absorption of food and nutrients can result in a diarrhea state. Diagnosis In order to diagnose the cause of chronic diarrhea, a rather extensive work-up may be necessary. First of all it includes a careful history and physical examination. Various tests are employed, including blood counts, serum chemistries, liver function and thyroid tests, urine evaluation, stool examination for bacteria as well as parasites and blood and a possible stool collection for fat or electrolytes.  Colonoscopy and/or upper endoscopy are frequently employed to evaluate the inside of the gastrointestinal (GI) tract and take specimens if necessary. Occasionally, upper or lower GI x-rays are also employed, as well as abdominal and pelvic sonography or CT scans of the abdomen. Treatment There is no one treatment for chronic diarrhea. The approach is dependent upon the actual cause, so once a work-up is completed, therapy can be directed at the specific cause for the chronic diarrhea. In rare cases, no cause is determined – this is called a chronic idiopathic diarrhea. In this case, dietary manipulation and various anti-diarrhea medications are employed.