There are many reasons for subrectal hyperdense shadow, usually considered to be related to rectal mass, feces, foreign body and so on. 1. Rectal mass: if the patient has constipation, blood in the stool and other manifestations, and at the same time, the anorectal fingerprinting can be found in the mass, and the CT considers the high-density shadow, it is necessary to be alert to whether it is a rectal mass. 2. Feces: if the patient has constipation and has not relieved stool before the examination, the patient can be asked to empty the stool, such as the disappearance of the high-density shadow after the evacuation of the stool, considering that it is related to fecal stone. 3. Foreign body: If there is a history of foreign body swallowing before the examination, such as coins, beer bottles, etc., or there is a foreign body stuffed from the anus, according to the size and shape of the hyperdense shadow to identify. If the rectal hyperdense shadow is considered, it is necessary to consult a doctor for further clarification of the etiology.