Rectal cancer refers to cancer occurring between the sigmoid-rectal junction and the dentate line, and its examination items are as follows: 1. Rectal finger examination can diagnose most of rectal cancers, but in some patients, if the tumor is located in high rectum, it is impossible to reach the tumor by rectal finger examination, and further proctoscopic examination should be done; 2.Fiber colonoscopy: observe the location and scope of lesion, and do pathological biopsy; 3.Pathological examination: do tumor biopsy under colonoscopy, confirm the diagnosis by pathology, and grade the tumor; 4.Laboratory examination: including blood biochemistry such as blood routine and liver and kidney function, and tumor markers, etc. A few patients with rectal cancer may show positive CEA; 5. Imaging tests: including frontal and lateral chest films, rectal imaging, abdominopelvic CT or MRI, rectal or abdominopelvic ultrasound. Rectal barium enema imaging can determine the location and scope of lesions; CT or MRI of abdomen and pelvis can determine the extent of tumor invasion and the presence of lymph node metastasis and liver metastasis; rectal ultrasound can determine the stage of primary tumor and surrounding lymph node metastasis; abdominal ultrasound can examine the lymph nodes adjacent to the abdominal aorta and liver metastasis, etc.