[Chronic diarrhea: a difficult diagnosis. A rare cause: lymphocytic colitis]

Lymphocytic colitis is a clinicopathological entity, characterized by chronic watery diarrhea, not bloody. Previously termed microscopic, it is now named lymphocytic for histological features, the most important seems to be the diffuse infiltration of intraepithelial lymphocytes, that must be investigated in multiple biopsies during colonoscopy. This review evidences that during endoscopy the mucosa is normal, but this does not exclude a biopsy, only way for take a diagnosis. Ethiologies are unknown too although a correlation with autoimmune diseases as possible. Lymphocytic colitis is a definition histological entity, while the term ''microscopic'' includes different histological entities under the same ''umbrella'', in relation to the concept of no macroscopic changes and multiple different histological specimens. The treatment is based for the first time on mesalazine or sulphasalazine and then in case of non responders, on corticosteroids.