What is the cause of abdominal pain bleeding before defecation

If the patient has abdominal pain and bleeding before defecation, the common reasons are as follows: First, if the patient eats unclean food, causing acute gastroenteritis, it will cause abdominal pain, and sometimes it will show hematochezia, and should be actively given drug treatment. Second, if the patient has ulcerative colitis, it is an autoimmune disease, sometimes it will cause abdominal pain, sometimes inflammation invades the blood vessels of the submucosa and also causes hematochezia, bright red or dark red, generally not mixed with feces. Third, if the patient has intestinal malignant tumor causing intestinal obstruction, fecal excretion is not smooth, it will also cause abdominal pain, abdominal distension, etc. If combined with intestinal perforation, it will also cause severe pain in the whole abdomen, fecal stimulation cancer will cause hematochezia.