Haemorrhoids (piles) are lumps occurring inside the anal canal (back passage) which contain swollen and enlarged blood vessels. They develop when the supporting tissue of the anal canal weakens so that the lining of the rectum (the end of the large bowel that is attached to the anus) bulges into the anal canal.
Blood vessels inside the haemorrhoids then begin to enlarge, causing symptoms such as bleeding, pain and discomfort. Haemorrhoids often go away without any treatment. However, if you notice blood when you have a bowel motion, it is always best to get it checked out by a doctor.
Sometimes an ‘external’ haemorrhoid can develop. It has similar symptoms. It develops when a vein bursts under the skin on outside edge of the anus, causing a painful lump to develop under the skin. If a blood clot forms inside the lump, it can be extremely painful.
Sources: Australian Family Physician (Publication - Daniel WJ., Anorectal pain, bleeding and lumps), Colorectal Surgical Society of Australia and New Zealand (Haemorrhoids. Modern management), NHS Choices (UK) (Piles (haemorrhoids), Piles (haemorrhoids) - Treatment)
Last reviewed: July 2015