Hemorrhoids are swollen veins that develop in the anus or rectum. While internal hemorrhoids form inside of the rectum, external hemorrhoids develop outside of the anus. Both types of hemorrhoids may cause pain, itching and bleeding. Excessive straining--for example, during labor or a bowel movement--or prolonged interruption of the blood flow into and out of veins in the pelvic region--for example, as a result of excessive abdominal fat or prolonged sitting--may increase pressure on the veins around the anus or rectum, causing them to swell.
Chronic Abnormal Bowel Habits
Chronic constipation or diarrhea can cause or exacerbate hemorrhoids by putting undue pressure on the blood vessels in the anus or rectum. Pressure on the veins may restrict blood flow, causing blood to stagnate and vessels to become inflamed. Straining during a bowel movement, in particular, may aggravate blood vessels in the lower rectum. According to Harvard Health Publications, sitting for extended periods on the toilet can also impair blood supply in the anal region, causing hemorrhoids to develop or worsen. Those who consume a diet high in fat and low in fiber may be more likely to have chronic constipation or diarrhea and are therefore at greater risk of developing hemorrhoids, according to eMedTV.
Excess Weight and Pregnancy
Individuals who carry excess weight are at greater risk of developing hemorrhoids. For example, according to FamilyDoctor.org, obese people may develop hemorrhoids as a result of the strain of carrying too much weight in the abdominal region.
Weight gain associated with pregnancy may also cause hemorrhoids by putting abnormal strain on the blood vessels in the lower abdomen and pelvic area. As the uterus expands to accommodate the growing fetus, it can put pressure on and inflame the veins around the anus, causing hemorrhoids to develop. According to the March of Dimes, hormonal changes during pregnancy may also affect veins in the lower rectum, causing them to dilate and swell. Pregnant women who suffer from constipation may develop worsening hemorrhoids from straining during bowel movements. Straining during labor and delivery can also cause or exacerbate hemorrhoids.
Advancing Age
According to Harvard Health Publications, normal aging is a cause of hemorrhoids. The muscles and connective tissue in the rectum and anus naturally weaken and stretch over time. As a result, they may become unable to support nearby blood vessels, which can interfere with normal blood flow through the veins. Pooling blood may cause the veins may swell, causing hemorrhoids to develop and prolapse, or bulge outward from the anus because of the weakened surrounding tissue.
