Ultrasonography (US) is a useful tool in the assessment of activity in ulcerative colitis (UC). Different studies have reported that US can correctly define the extension of UC, and the degree of bowel wall thickness is correlated to the clinical activity. The examination with a linear transducer in tissue harmonic imaging is indispensable to the detail evaluation of bowel wall stratification. In the Doppler mode, widespread mural vessels are found in active UC. Without contrast agent, Advanced Dynamic Flow can depict tiny vessels in the submucosa with an Aplio80 scanner (Toshiba, Japan), and improve the measurement of arterial blood flow velocity. Therefore, US should be considered as a reliable method for the evaluation of disease activity in UC.