Blood in the stool in the morning and not in the afternoon can be seen in a variety of diseases, which may be caused by bleeding in the upper and lower gastrointestinal tract or systemic diseases. 1. Upper gastrointestinal diseases: esophageal diseases such as ruptured varices in the fundus of the esophagus and esophageal foreign bodies, peptic ulcers, and bile duct stones can lead to blood in the stool. 2. Lower gastrointestinal diseases: hookworm, acute bacillary dysentery, colon polyps and other intestinal diseases; rectal polyps, hemorrhoids, anal fissure, anal fistula and other rectal-anal tube diseases may also lead to blood in the stool in the morning. 3. Systemic diseases: such as leukemia, sepsis, uremia, thrombocytopenic purpura, vitamin C and K deficiency and other systemic diseases can also lead to blood in the stool from time to time. In addition, gastric cancer and rectal cancer may also lead to blood in stool in the morning and not in the afternoon. You cannot judge the disease by blood in stool alone, and if accompanied by other discomforts, it is recommended to consult a doctor in time so as to avoid delaying the condition.