Self-testing of bowel cancer generally refers to judging whether one is experiencing relevant symptoms as a basis for going to the hospital for further examination and treatment. Bowel cancer generally refers to colorectal cancer, including colon cancer and rectal cancer, so it is also called colorectal cancer, while rectal cancer is usually most common with rectal adenocarcinoma. Colorectal cancer starts insidiously, and patients can detect themselves through the following symptoms: 1. defecation: including changes in defecation habits and stool properties, which is the earliest symptom of colorectal cancer, and can appear as bloody stool or positive stool occult blood test, and the specific amount of bleeding is often related to the size of the cancer and the depth of invasion. Patients may also have persistent constipation and thin stools. Patients with right-sided colorectal cancer may also have diarrhea or alternating symptoms of diarrhea and constipation, without obvious mucus-purulent stool; 2. Abdominal pain: right-sided colorectal cancer is the most common, with dull pain in the right abdomen, which may radiate to the upper abdomen. Patients may also have postprandial abdominal pain, which is mainly related to the enhancement of gastrocolic reflex, and when complicated with intestinal obstruction, it may cause increased abdominal pain or paroxysmal colic; 3. Masses: most patients with colorectal cancer may have hard nodules, which are often found during rectal examination, and bloody mucus can be seen on the finger sleeve. According to the change of cancer location in the middle and late stages, masses often appear in the abdomen, while patients with right-sided colorectal cancer often have abdominal masses and systemic symptoms such as anemia and emaciation as the main manifestations; 4. Systemic symptoms: patients with right-sided colorectal cancer often have symptoms such as anemia and low fever, while patients with advanced stage can see symptoms such as progressive emaciation and fluid in the abdomen. Patients with left-sided colorectal cancer mainly show symptoms such as eczema, diarrhea, constipation, intestinal obstruction, etc.; 5. Complications: advanced patients may have intestinal obstruction, intestinal bleeding and cancer metastasis to the abdominal cavity and other related complications. When patients have the above symptoms, they should go to hospital immediately. Common examination methods include colonoscopy, X-ray barium enema, CT colon imaging, etc., among which colonoscopy has diagnostic significance. Fecal occult blood test is not specific for colorectal cancer, but it can be used as a basis for screening and early diagnosis. Meanwhile, patients with inflammatory bowel diseases such as ulcerative colitis, colorectal adenoma, long-term smoking or alcohol consumption, as well as chronic diarrhea, chronic constipation, chronic appendicitis or family history of colorectal cancer need to be vigilant.