Hemorrhoids are varicose veins of the rectum. The hemorrhoidal veins are sited in the lowest area of the rectum and the anus. Sometimes they swell, so that the vein walls become stretched, slim, and irritated b passing bowel movements. When these veins bleed, itch, or hurt, they are known as hemorrhoids, or piles. Hemorrhoids are divided in two general categories: internal and external.
Formation of External hemorrhoids
Veins in the rectum and anus are under considerable pressure whenever a stool is passed. Pushing or straining may cause veins in the rectal wall to lump, creating clusters of swollen, or dilated, veins called hemorrhoids. Internal hemorrhoids can form anywhere inside the anal canal, while external hemorrhoids are visible, or just below, the opening of the anus.
External hemorrhoids are situated within the anus and are usually painful. If an external hemorrhoid prolapses to the outside you can see and feel it. Blood clots sometimes form within prolapsed external hemorrhoids, causing an extremely painful condition called a thrombosis. If an external hemorrhoid becomes thrombosed, it can look rather frightening, turning purple or blue, and possibly bleeding. Despite their appearance, thrombosed hemorrhoids are usually not serious and will resolve themselves in about a week.
Symptoms of external hemorrhoids
The symptoms of external hemorrhoids are different than the symptoms of internal hemorrhoids. External hemorrhoids can be felt as bulges at the anus, but they usually cause few of the symptoms that are typical of internal hemorrhoids. External hemorrhoids tend to be painful. Sometimes blood may pool in an external hemorrhoid and form a clot (thrombus), causing severe pain, swelling and inflammation. When irritated, external hemorrhoids can itch or bleed.