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.

        Key words: ulcerative colitis – morphological diagnosis – sets of biopsies of the mucosa of the large intestine – diffuse and focal type of inflammation in UC – repeated bioptical examination of the large intestine.