The term hemorrhoids refers to a condition in which the veins around the anus or lower rectum are swollen and inflamed.
Hemorrhoids are common in both men and women. About half of the population has hemorrhoids by age 50.
There are several groups of veins that surround the rectum and anus -- one group is known as internal hemorrhoidal veins, the other is known as external hemorrhoidal veins. The underlying cause of hemorrhoids is increased pressure within these veins.
There are two types of hemorrhoids, and each type is named for the veins that are affected. The internal type is caused by increased pressure within the internal hemorrhoidal veins; the external type is caused by increased pressure within the external hemorrhoidal veins.
There are a number of conditions that can increase the pressure within the hemorrhoidal veins. While these conditions are not causes of hemorrhoids, they are considered risk factors.
Risk factors include:
- Straining to move stool, or other poor bowel habits such as sitting for long periods
- Pregnancy
- Aging
- Chronic constipation or diarrhea
- Anal intercourse
- Cirrhosis
- Obesity
- A high-fat, low-fiber diet.
(Click Causes of Hemorrhoids for more information.)