Hidden pain in the left lower abdomen that turns red after a bowel movement may be caused by colitis, intestinal tuberculosis, colon cancer and other diseases, which can be treated by drugs and surgery. 1. Colitis: caused by various factors such as immunity, infection, etc. It can be induced by mental tension and psychological pressure. It mostly causes pain in the left lower abdomen or small abdomen and bloody stool. Colitis can be treated by taking medications such as sulfasalazine. The drug may cause sore throat and other adverse reactions, allergy, pregnant women, lactating women, etc. are prohibited. 2. Intestinal tuberculosis: generally caused by tuberculosis mycobacterium infection, can cause vague pain, pressure pain and other symptoms, and accompanied by blood in the stool, can be treated with drugs such as rifampicin. The drug may cause nausea, diarrhea and other adverse reactions. It is forbidden for allergy, severe liver insufficiency, bile duct obstruction and pregnant women within 3 months. 3. Colon cancer: It is a malignant tumor of digestive tract born in colon, which can cause abdominal pain and discomfort, pus and blood and abdominal mass. It is usually treated by surgery to remove the tumor, and can be combined with radiotherapy and chemotherapy. In order to diagnose what kind of disease is the symptom of hidden pain in the left lower abdomen and reddish stool, you need to go to the hospital for appropriate examination, and only after diagnosis can you treat the symptoms. If you need to use drugs, please consult your physician beforehand.