Bright red blood in the stool is mainly considered to be bleeding from haemorrhoids or anal fissures. The accompanying symptoms, in addition to blood in the stool, may be accompanied by prolapse of the anal swelling and localised pain in the anus, and the presence of a definite haemorrhoid nucleus or fissure can be seen on examination.
Pus and blood in the stool may be due to colitis or ulcerative colorectitis, and is usually accompanied by varying degrees of abdominal pain, increased frequency of bowel movements and diarrhoea. Dark red, dark bloody stools may be due to a tumour of the intestine, usually in the middle to late stages, accompanied by weight loss and changes in bowel habits. It may even cause intestinal obstruction if the tumour grows to a certain extent.
It is important to note that some patients with rectal cancer may present with fresh blood in their stools, which can be extremely easy to confuse with bleeding haemorrhoids.