There are many causes of abdominal pain with blood in stool, such as colitis, rectal cancer, etc. The details are analyzed as follows: 1. Colitis: patients usually consult the doctor with symptoms such as persistent abdominal pain, diarrhea, difficulty in defecation, blood in stool, etc., and the blood in stool is mostly manifested as mucous blood stool. 2. Rectal cancer: it refers to epithelial malignant tumor originated from rectal mucosa. Early symptoms of rectal cancer are not obvious, but in late stage, frequent bowel movement, change of bowel habit and lower abdominal pain may occur. The surface mucosa of rectal cancer is easy to erode, which may lead to bleeding during defecation, manifested as blood in stool, often accompanied by mucus. To sum up, there are many causes of abdominal pain with blood in stool, so it is necessary to consult the doctor in time, complete the relevant examination, make a clear diagnosis, and follow the doctor’s instruction for treatment.