What disease causes painless rectal bleeding?

Painless hematochezia is a common clinical symptom with multiple causes, mainly including internal hemorrhoids, intestinal polyps, colonic or rectal tumors, and gastrointestinal bleeding. As the most common cause, internal hemorrhoids typically present with bright red blood in or after stool, without significant pain. Intestinal polyps also may cause painless hematochezia, with bright red blood that does not mix with the stool. Colonic or rectal tumors may bleed when ulcerated, and the amount of bleeding can be substantial, thus requiring serious attention. In addition, gastrointestinal bleeding, especially massive upper gastrointestinal bleeding, can also manifest as painless hematochezia, although the stool is usually black or tarry in such cases. Patients experiencing painless hematochezia should seek timely medical attention to determine the underlying cause through physical examination, laboratory tests, and imaging studies, so that appropriate treatment measures can be taken. For benign conditions such as internal hemorrhoids, medical treatment or surgical intervention is usually effective. However, for malignant diseases like colonic or rectal tumors, a comprehensive treatment plan must be formulated according to the patient's specific condition. The specific diagnosis and treatment plan must be developed by a qualified physician based on the individual patient's circumstances.