What is the cause of hemorrhoids? Before discussing hemorrhoids causes, lets have a look at what hemorrhoids are.Hemorrhoids or piles are expanded blood vessels in the anus. They are caused by too much pressure in the rectum which causes the vein to expand and form a lump called a hemorrhoid. Read on for the causes of hemorrhoids.CausesThe main is the fact that the condition is hereditary, and some people are more prone to getting it than others. For people who have hemorrhoids in their family.