The collar button ulcer. A radiologic-pathologic correlation

The collar button-shaped ulcer is a distinctive radiographic manifestation of inflammatory disease of the GI tract. Its hallmark is mucosal ulceration with undermining submucosal extension limited by the relatively resistant underlying muscle wall. Such a process is commonly associated with ulcerative colitis where it may be seen diffusely in advanced stages of the acute disease. Occasionally, however, it may be seen in any ulcerating inflammatory disease. In the more aggressive transmural diseases, it is likely to be a localized and transient phenomenon. The same pathophysiological mechanism gives rise to the common appearance of benign ulceration anywhere in the GI tract and, particularly, in the undermined gastric ulcer.