It may be caused by a pelvic mass or an intra-abdominal tumor. There are many types of pelvic masses, including ovarian cysts, lymphoma, etc. In the early stage, it can be manifested in the pelvic cavity with vague pain and masses, with the prolongation of the disease history, the masses can gradually increase in size, or the tumor presses the rectum to appear difficult to defecate or thin stools, etc. If necessary, it can be further clarified by doing CT or ultrasound in the abdomen. If it is considered to be caused by a mass in the abdominal cavity, surgical resection is also needed. If the colon tumor, usually manifested in the sigmoid colon, rectum or ileocecal region can lead to swelling in the lower abdomen, and local pressure pain. You can perform colonoscopy to further define the location of the mass, and also need to do abdominal CT to judge the lymph nodes around the colon, after the diagnosis is clear, it is recommended to perform radical surgery for colon tumor.