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Understanding Hemorrhoids -- the Basics

What Are Hemorrhoids?

Hemorrhoids are swollen blood vessels of the rectum. The hemorrhoidal veins are located in the lowest area of the rectum and the anus. Sometimes they swell so that the vein walls become stretched, thin, and irritated by passing bowel movements. Hemorrhoids are classified into two general categories: internal and external.



Internal hemorrhoidslie far enough inside the rectum that you can't see or feel them. They don't usually hurt because there are few pain-sensing nerves in the rectum. Bleeding may be the only sign that they are there. Sometimes internal hemorrhoids prolapse, or enlarge and protrude outside the anal sphincter. When this happens, 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 often be gently pushed back into place.

External hemorrhoids lie within the anus and are usually painful. If an external hemorrhoid prolapses to the outside (usually in the course of passing 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 could possibly bleed. Despite their appearance, thrombosed hemorrhoids are usually not serious but can be painful. They will resolve themselves in a couple of weeks. If the pain is unbearable, your health care provider can remove the thrombosed hemorrhoid, which stops the pain.

Anal bleeding and pain of any sort should be evaluated by a qualified health care provider; it can indicate a life-threatening condition, such as colorectal cancer. However, hemorrhoids are the No. 1 cause of anal bleeding and are rarely dangerous, but a definite diagnosis from your health care provider is important.

What Causes Hemorrhoids?

About 30% to 40% of the people in the U.S. will suffer from hemorrhoids at some point in life; for most, this will happen between ages 20 and 50. Researchers are not certain what causes hemorrhoids. "Weak" veins -- leading to hemorrhoids and other varicose veins -- may be inherited.

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