Pathomorphology of ulcerative colitis. Nippon Rinsho. 2005 May;63(5):763-9.

Microscopic and macroscopic appearances of ulcerative colitis (UC) by its phase of inflammation were summarized. The most characteristic microscopic findings of active phase UC is diffuse lymphoplasmacytic infiltration, essentially associated with basal plasmacytosis. Although inflammation of UC is basically limited to the mucosa, active inflammation extends into the submucosa in some instance, and acute ischemic change is overlapped to cause toxic megacolon. In remission phase, inflammation is reduced and goblet cell mucus is fully recovered but evidences of the past inflammation such as irregular shape and disarrangement of crypts, Paneth cell metaplasia, thickening of the muscularis mucosae and discrepancy between the crypt base and the muscularis mucosae are usually demonstrated. Macroscopic appearances of UC reflect its microscopic findings such as degree of inflammation, whether inflammation is (was) limited to the mucosa or extend(ed) into the submucosa. Active phase is classified into erythematous, spongy, granular, pseudopolyp, ulcerative, and fulminant (toxic megacolon) type. In the former two types, inflammation is limited in the mucosa, and the latter two types are associated with ischemic change. In remission phase, erythematous and spongy types recover to the almost normal looking mucosa or fine granular mucosa with preservation of mucosal folds, granular type recovers to granular, fine granular or flat atrophic mucosa without preservation of mucosal folds, and pseudopolyp type recovers to mucosa with inflammatory polyposis.

Ulcerative colitis--contemporary morphological criteria.Cesk Patol. 2004 Oct;40(4):154-8.

Regular bioptical examinations of patients with ulcerative colitis (UC) performed in recent years show that the inflammatory changes of the mucosa of the large intestine are not necessarily diffuse, and that their extent may vary in the course of the disease. To establish the diagnosis of UC and to assess the treatment efficacy it is important to examine histologically multiple mucosal specimens from different levels of the large intestine. In our series of 27 patients with ulcerative colitis (18 men and 9 women at the age of 17 to 76 years), active or active and inactive pancolitis was diagnosed in 25 cases (93%). In 11 of these, the whole of the large intestine was affected. Two patients showed diffuse pancolitis without caecal involvement, in 5 cases there was inactive inflammation in the rectum or in the sigmoid colon. Seven patients had active colitis of the rectum and sigmoid. In another 2 patients (7%), the inflammation was limited to several segments of the large intestine only (the descending colon, and the descending and transverse colon). On bioptical examination of 6 patients repeated after 2-29 months (mean 14 months), there were changes in the distribution and appearance of the inflammation. Thus our findings correspond with the results of previous studies: UC does not always affect the mucosa of the large intestine diffusely. Further, the extent and distribution of inflammatory changes vary in the course of the disease.