Possible causes of sudden blood in stool without other symptoms include: dry stool, hemorrhoids, rectal polyps, anal papilloma, etc. 1. Dry stools: If the patient has dry stools, the lower digestive tract may be damaged during defecation, resulting in sudden blood in stool. 2. Hemorrhoids: injury to the varicose veins of the anal canal during defecation can also result in asymptomatic and sudden blood in the stool. 3. Rectal polyps: rectal polyps have many causes, if the patient has rectal polyps, it may be due to the damage in the process of defecation and the sudden asymptomatic blood in the stool. 4. anal papilloma: with the lesion gradually increase, defecation can damage the lesion tissue, also can cause asymptomatic sudden blood in stool. If the symptoms can not be relieved in time, the patient should consult a doctor in time to avoid delaying the condition.