Constipation and diarrhea are common diseases: irritable bowel syndrome, proctitis and colorectal cancer. 1. Irritable bowel syndrome Irritable bowel syndrome (IBS) is a kind of functional bowel disease with abdominal pain and change of bowel habit without organic disease. The common symptoms are pain in the lower abdomen and left lower abdomen, change in the number of bowel movements, change in the character (appearance) of feces, which may be constipation and diarrhea. 2. Proctitis Proctitis is an inflammatory disease that occurs in the rectum. It can be manifested as urgency, abdominal pain, constipation, diarrhea or alternating between constipation and diarrhea. 3. Colorectal cancer Including hereditary and non-hereditary, common colorectal adenocarcinoma can manifest as abdominal pain, change of bowel habit and fecal character, rectal and abdominal mass, emaciation, malignant disease, etc. It can manifest as constipation and diarrhea. If there is constipation and diarrhea, it is recommended to go to the hospital in time for diagnosis and treatment with the help of doctor.