Two of the most common types of hemorrhoids are external and internal hemorrhoids. External hemorrhoids are those that occur outside of the anal opening. They are usually painful, and are often accompanied by itching, swelling, and burning sensation.
Internal hemorrhoids are those that occur inside the rectum. As this area lack sensitive nerve endings, internal hemorrhoids are usually not painful and most people are not aware that they have them. Internal hemorrhoids, however, may bleed when irritated.
Untreated internal hemorrhoids can lead to two severe forms of hemorrhoids: prolapsed and strangulated hemorrhoids. Prolapsed hemorrhoid is an internal hemorrhoid that are so distended that it is pushed outside of the anus. If the anal sphincter muscle goes into spasm and trap the prolapsed hemorrhoid outside of the anal opening, the supply of blood is cut off, and the hemorrhoids become a strangulated hemorrhoid.
See also: Preparation HTypes and symptoms of Hemorrhoids