Early lesions of the colonic mucosa possibly developing into ulcers of ulcerative colitis

Biopsy specimens from the colonic mucosae of patients with ulcerative colitis (UC) were examined using both transmission and scanning electron microscopes (TEM and SEM) in order to elucidate the fine pathological changes in the mucosae preceding obvious ulcers. The interglandular surface epithelium exhibited distension of the intercellular spaces, where both blood cells and plasma had infiltrated. Partial destruction of epithelial cells was also seen. Thick fibrous layers of the basement membranes of the interglandular epithelium were rough and porous, with fenestrations. Partial loss of the fibrous layers was also seen, which suggested mucosal ulcers nearby. In the lamina propria, congested blood vessels with ruptured walls containing blood cells were frequently seen. The perivascular tissues were edematous with large amounts of exudate, containing many blood cells. The subsequent, longtermed intramucosal retention of infiltrated blood may thus lead to mucosal lesions, including cell death and destruction, and, as a result, prolong the severe lesions in the mucosae with inflammation.