CURRENT CONCEPTS OF THE PATHOGENESIS AND PATHOLOGY OF INFLAMMATORY LESIONS OF THE INTESTINE.

The histopathologic lesions of regional enteritis and ulcerative colitis, particularly in their early stages, are distinct and distinguishable, irrespective of the sites that are involved. Regional enteritis is characterized by lymphangiectasis, lymphedema, lymphoid hyperplasia, and granulomatous inflammation of the submucosal and subserosal layers of intestine, whereas chronic ulcerative colitis is an exudative, ulcerative disorder of the mucosal layer that commences with "crypt abscesses" and only in its later stages progresses to deeper coats of the wall.Electron microscopy of a rectal biopsy from a juvenile patient with chronic ulcerative colitis for five years disclosed a labyrinthine system of clefts and compartments between columnar, mucosal epithelial cells. Regenerated colonic epithelial cells were of primitive, germinal type and featured a "vesicular" rather than a "goblet" pattern of mucus secretion. Clusters of small "clavate fimbriae" projected from the tips of microvilli. Each of these newly recognized substructures measured 30 to 60 mmu. in diameter, and was enclosed by a tri-laminar "unit membrane", derived from the surface plasma membrane of the cell.