RESUMO
There are so many well known causes of diarrhea up to now that the simplest way to study the lesions to which they may associated, is by considering the following groups. 1. A series of diseases in which no anatomical alterations are found, or if present they are insignificant. 2. Those with definite but non-specific pathological changes. 3. Diseases in which pathological changes are consistent but not diagnostic with the clinical diagnosis. 4. Those in which pathognomic lesions are present. It is pointed out that in the first group some diseases can be diagnosed by the use of highly specialized methods (Ex. Disaccharidase deficiency). Adequate knowledge of the pathological entity, both clinically and morphologically is the only way to take advantage of a precious diagnostic medium, such as the biopsy, which otherwise might be useless or even harmful.