Hemorrhoids are swollen veins. Each of us has veins around the anus that tend to stretch under pressure. One set of veins is inside the rectum (internal) and another is under the skin around the anus (external). Hemorrhoidal tissue is thought to be helpful in holding back stool at rest and in cushioning the sphincter muscles when we empty our bowels.
When these veins swell and bulge, they are called "hemorrhoids" or "piles." Swelling can be caused by straining to move your bowels, from sitting too long on the toilet, or from other factors such as pregnancy, obesity or liver disease.
The most common symptom of internal hemorrhoids is bright red blood covering the stool, on toilet paper or in the toilet bowl. Bleeding starts when the swollen veins are scratched or broken by straining or rubbing. This can be aggravated by medicines that thin the blood. An internal hemorrhoid may protrude through the anus outside the body, becoming irritated and painful. This is known as a protruding or prolapsed hemorrhoid.
Symptoms of external hemorrhoids may include painful swelling or a hard lump around the anus that results when a blood clot forms. This condition is known as a thrombosed external hemorrhoid.
Irritation around the anus can cause bleeding and/or itching, which may produce a vicious cycle of symptoms. Draining mucus or stool residue may cause itching. The technical term for this itching is pruritus ani and it can be caused by either excessive rubbing or cleaning around the anus or poor hygiene with residual stool around the anus.
How Common Are Problems with Hemorrhoids?
Hemorrhoid problems are very common in men and women. About half of all people have noticeable hemorrhoids by the age of 50. Many people have occasional bleeding from hemorrhoids, but most often the bleeding is self-limited. Women may begin to have problems during pregnancy. The pressure of the fetus in the abdomen, as well as hormonal changes, causes hemorrhoidal veins to enlarge. These veins also are placed under severe pressure during the birth of the baby. For most women, such hemorrhoids are a temporary problem.
It is not normal to pass blood, so notifying your doctor of bleeding is important. Your doctor will likely exam your anus and rectum and possibly further examine the bowel. In the absence of a clot (thrombosis), the soft cushion of hemorrhoid tissue cannot be readily felt by examining with a finger, so examining the anal canal and colon with a flexible scope (colonoscopy or sigmoidoscopy) may be recommended.
American Gastroenterological Association. (April 25, 2010). Living with Hemorrhoids.
From http://www.gastro.org/patient-center/digestive-conditions/hemorrhoids web.