Diagnosis and therapy of acute and chronic diarrhea.

Many patients who present with acute or chronic diarrhea do not have an important organic disease. Most have functional diarrhea. The history, clinical examination, and initial laboratory studies should lead to a provisional diagnosis with respect to organic or functional origin and help define whether the disease affects the small or large intestine. Specific studies are then obtained to define organic causes. The most common causes of acute diarrhea are infections and drugs, while the most common causes of chronic diarrhea are inflammatory bowel disease, malabsorption, parasitic infections, carcinoma of the large bowel, and metabolic diseases. Clinicians should remember that patients with functional diarrhea are as prone to other severe disease as the rest of the population and avoid allowing the functional problem to mask other signs.