Unexpected Radiologic Findings for a Casting Type of Radiolucent Colorectal Foreign Body Composed of Polyurethane Foam

Radiologic diagnosis of colorectal foreign bodies is usually not very difficult, because inserted materials are often clearly visible on plain abdominal radiographs. However, when they are radiolucent, a plain abdominal radiograph has been reported to be useless. As radiolucent colorectal foreign bodies appear as radiolucent artificial contours or air-trapped materials in the pelvis, almost always the diagnosis itself can be made by careful evaluation of plain abdominal radiographs. We encountered a case of casting type of radiolucent colorectal foreign body formed from polyurethane foam. It presented us with unexpected radiologic findings and led to diagnostic difficulties.