Haemorrhoids are foreign body growths that occur inside the rectum, at the end of the rectum, and can easily induce painful sensations. In general, most pain induced by internal haemorrhoids is affected by infection and thrombotic factors; pain induced by external haemorrhoids is associated with mechanical injury and acute venous thrombosis.
Pain can also be induced when internal haemorrhoids develop to the point of severity, causing the haemorrhoid to prolapse and become embedded.