The main causes of blood in stool with anal pain are: 1. Hemorrhoids, mainly internal hemorrhoids, are mainly due to varicose veins around the anus. The fissure is mainly caused by dry stool, defective development of the anal sphincter, and spasm of the anal sphincter, resulting in tearing of the anal sphincter during stool and destruction of the perianal tissue. 3, acute enteritis, mainly due to bacteria, viruses and other pathogens into the intestinal tract, resulting in intestinal mucosa congestion, edema and mucosal damage and increased number of stools, anal cramping and pain, stools can be with pus and blood.