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Diarrhea is usually defined as multiple loose or watery bowel movements, many times more frequent than one’s usual pattern.  Some people describe diarrhea, but are only having one loose stool per day. This is a change in their bowel habit, but not really diarrhea.

There are many causes for diarrhea, but on this page I will review some of the more common causes for both acute (sudden onset) and chronic (long lasting) diarrhea.

1. Acute Diarrhea
a. Infections: the most common causes are food poisoning due to ingested toxins, bacteria, viruses and parasites (like giardia, amebas, cyclospora). These usually resolve on their own within 1-7 days. Treatment is most helpful with some of the bacteria and parasites. (Parasitic symptoms may last for weeks or months.)
b. Gastrointestinal Disorders: such as partial bowel obstruction (with prior surgeries), fecal impaction (especially in nursing home patients) ischemic colitis (in middle aged women), diverticulitis and the initial attacks of ulcerative colitis and Crohn’s disease.
c. Drugs: side effects of many drugs can include diarrhea. Some examples include: anti-hypertensives, antibiotics, iron, some anti-depressants, diabetic and arthritis medications. Some patients are inadvertently taking laxatives or sugar-free foods with sorbitol that cause diarrhea.
d. Antibiotic Colitis: doesn’t occur when taking the antibiotics, but usually begins within 1-4 weeks after finishing a course of antibiotic treatment. The diarrhea may be severe, and requires medical treatment most of the time.
e. Unusual Causes: like hyperthyroidism or carcinoid syndrome.

2. Chronic Diarrhea
This is when the loose bowel movement persists for more than 3 weeks. The possible reasons are listed below:
a. Inflammatory bowel diseases: things such as ulcerative colitis, Crohn’s disease, microscopic colitis (lymphocytic and collagenous colitis).
b. After Bowel Resection or Radiation: after gastrectomy, cholecystectomy (gallbladder removal), vagotomy, or radiation treatment that effects the bowel.
c. After or during chemotherapy.
d. With the irritable bowel syndrome (IBS).
e. Celiac Sprue
f. Unusual causes: certain cancers, unusual tumors, thyroid dysfunction, malabsorption, scleroderma, diabetes and pancreatic problems.

Diarrhea can be treated in most cases. Finding the cause, however, is the key. Having bloody diarrhea, abdominal pain or fever with loose stools is most alarming, and requires prompt medical attention. Lab tests of the stool and blood, as well as Colonoscopy may be warranted. These can only be considered after a thorough history and physical exam.

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