直肠是大肠的末端,上接乙状结肠,下接肛管,直肠全长平均12cm。肛管为直肠下端,长约2～3cm,肛管外口为肛门。直肠内粘膜呈暗红色,光滑柔润,粘膜较厚,血管丰富,而肛管内肛柱有丰富的静脉丛,壁薄无瓣,容易瘀血扩张。一旦患病容易便血。因此,便血就成为直肠、肛管疾病的 The rectum is the end of the large intestine, followed by the sigmoid colon, under the anal canal, the average length of the rectum 12cm. Anal canal is the lower end of the rectum, about 2 ~ 3cm, the anus for the anal orifice. Rectal mucosa was dark red, smooth and soft, mucous membrane thick, rich in blood vessels, anal anal plexus has rich veins, thin wall without flap, easy blood stasis expansion. Once the illness easy blood in the stool. Therefore, the blood in the stool to become rectum, anal canal disease