Blood in the stools is always abnormal and should be properly assessed by a doctor.
Blood may manifest in various forms, from fresh red blood, to dark red blood, to black-coloured stools, to blood that cannot be detected with the naked eye. This is an indicator of the site of bleeding within the gastrointestinal tract and helps to direct the mode of investigation. Blackcoloured stools point to a possible source of bleeding within the stomach or small intestines (ie the upper gastrointestinal tract), while fresh or dark red blood suggest a possible source within the colon (or lower gastrointestinal tract).
The volume of blood in the stools determines the urgency of investigation as a large amount of blood being expelled per rectum may result in severe anaemia that may be life-threatening. On the other hand, even a small amount of blood in the stools may be due to underlying colorectal cancer and also warrants early investigation.
