Blood in the stool with left lower abdominal pain is commonly seen in two conditions: the first condition, ulcerative colitis, which is often a purulent blood stool with left lower abdominal pain. In addition, patients with a long course of the disease may also have symptoms of wasting. In the second case, malignant tumors of the intestine, the blood in the stool is often accompanied by a change in bowel habits or a change in the thickness of the stool. Further examination and laboratory tests are needed to confirm the clinical diagnosis. In addition, there are other causes of blood in the stool, such as bleeding hemorrhoids, often with blood in the stool, or bleeding after the stool. There is also bleeding from the gastrointestinal tract, and upper gastrointestinal bleeding can have black stools. Also, bleeding can occur from benign tumors of the intestines, such as adenomas of the intestines.