Reviewed by Brian R. Robinson, MD
Hemorrhoids occur when the veins in the rectum and anus become enlarged or dilated and stretch under pressure. This can result from a diet high in refined and processed food and low in grain and bulk forming foods. Hard, dry feces that have less bulk are more difficult to pass and strain the bowels. This increases the pressure in the veins around the anal canal and causes them to become enlarged and dilated. Pregnancy, heredity, aging, chronic constipation or diarrhea can also contribute to hemorrhoid formation. In adults, hemorrhoids are the most common cause of blood in the feces.
Most hemorrhoids occur inside the anus (internal hemorrhoids) but some develop outside the anus (prolapsed hemorrhoids). There is a line (the dentate line) in the anal canal that separates two types of anal skin, and while the skin above the dentate line is not sensitive to pain, the skin below this line is quite sensitive. Internal hemorrhoids occur above the dentate line and are, therefore, usually painless. They can cause bleeding or they may push (prolapse) out of the anal opening when they become quite large. External hemorrhoids occur below the dentate line and can become very painful. They are sometimes called skin tags, because they can be seen or felt as extra skin around the anus. External hemorrhoids can become very distressing when the blood in the external hemorrhoid clots and inflammation irritates the nearby pain-sensitive skin. This condition is called thrombosed external hemorrhoids and is extremely painful.
Hemorrhoids are very common in both men and women around the age of 50, and they occur most commonly in caucasians. During pregnancy, the weight of the fetus and childbirth can cause severe pressure on the abdomen and allow the hemorrhoidal vessels to enlarge. Fortunately, most pregnancy-related hemorrhoids are temporary.