Critères anatomopathologiques d'évolution des colites chroniques idiopathiques.

Idiopathic inflammatory colitis are diseases of remissions and exacerbations of various severity. The criteria of activity are based on a conjunction of clinical, radiologic, endoscopic and anatomopathological data. From the macroscopical point of view, they are different in ulcerative colitis and Crohn's disease. Ulcerative colitis is characterized by a diffuse and uniform mucosal inflammation; any biopsy outside an ulcerative area can be used to evaluate the inflammatory components which are in the acute phase (chronic active phase): oedema, vascular congestion and an inflammatory infiltrate composed of a mixture of lymphocytes, plasma cells and polymorphs with partial destruction of the glands (crypt abscesses). In the revolving phase, the inflammation regresses; the crypts are distorted, the crypt abscesses gradually disappear. In ulcerative colitis in remission, the inflammation vanishes but there is loss of parallelism and branching of the crypts. In Crohn's disease, the inflammation is often discontinuous and focal; biopsies must be taken from multiple sites. It is not rare to see a coincidence of lesions at different stages of activity. The criteria of activity are less reliable than in ulcerative colitis. Acute lesions present with oedema and infiltration of the lamina propria by polymorphs, neutrophils as well as eosinophils. Granulomas probably represent a particular reactional status. There features and number do not very significatively in the course of the disease