Background: ulcerative colitis is one type of IBD and its prevalence is increasing worldwide and in Egypt and the disease itself carries a lot of sufferings and burden on the patients due to its chronic course and periods of relapse, ulcerative colitis needs regular follow up and monitoring, the use of ultrasound is being increased in diagnosis and follow upof IBD patients as a simple, reliable and non-invasive method. Patients and methods: this study included a group of 30 ulcerative colitis patients in different disease activity and tested by the trans abdominal ultrasound to measure the wall thickness of sigmoid colon as marker of disease inflammation and activity. Results: the study showed that there is a significant difference in the colonic wall thickness between different disease activity and showed that ultrasound is sensitive to detect this change in colonic wall thickness. Conclusion: ultrasound in the hands of the trained personnel is a valuable tool to assess the activity of ulcerative colitis by detection of changes in the colonic wall thickness.