What are Hemorrhoids?
Hemorrhoids are varicose veins of the rectum. The hemorhoidal 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 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.
Internal hemorrhoids lie far inside the rectum that you can't see or feel them. They do not usually hurt, because there are few pain sensing nerves in the rectum. Bleeding may be the only sign of their presence. Sometimes internal hemorrhoids prolapse, or enlarge and protrude outside the anal sphincter. If so, you may be able to see or feel them as moist, pink pads of skin that are pinker than the surrounding area. Prolapsed hemorrhoids may hurt, because the anus is dense with pain-sensing nerves. They usually recede into the rectum on their own; if they don't, they can be gently pushed back into place. Most commonly the blood in stool caused by hemorrhoids is bright red but internal hemorrhoids can be reason for appearance of dark blood in stool.
External hemorrhoids are situated within the anus and are usually painful. If an external hemorrhoid prolapses to the outside (usually in the course of passing a stool) 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. If the pain is unbearable, your doctor can remove the thrombosis, which stops the pain, during an office visit.