Hemorrhoids (HEM-uh-roids), also called piles, are swollen veins in your anus and lower rectum, similar to varicose veins. Hemorrhoids have a number of causes, although often the cause is unknown. They may result from straining during bowel movements or from the increased pressure on these veins during pregnancy. Hemorrhoids may be located inside the rectum (internal hemorrhoids), or they may develop under the skin around the anus (external hemorrhoids).

Hemorrhoids are very common. Nearly three out of four adults will have hemorrhoids from time to time. Sometimes they don't cause symptoms but at other times they cause itching, discomfort and bleeding.

Occasionally, a clot may form in a hemorrhoid (thrombosed hemorrhoid). These are not dangerous but can be extremely painful and sometimes need to be lanced and drained.