Haemorrhoids, also known as piles, are swellings that develop from three pads or cushions of tissue that line the anal canal or back passage.

The tissue of the anus is rich in blood vessels.  If these become dilated and swollen, they may project into the anal canal or out of the back passage (a prolapse) to form visible swellings. Some people describe them as varicose veins of the anus.

Haemorrhoids tend to be caused by factors that cause the blood vessels to swell. These include anything that increases pressure inside the abdomen, such as constipation, pregnancy and being overweight.

Common symptoms are a swelling protruding from the anus, bleeding from the back passage, a mucus discharge and itching of the skin around the back passage.

For further information see the video on Haemorrhoids explaining the medical condition.