Hemorrhoids are enlarged veins in the anus or lower rectum. They often go unnoticed and usually clear up after a few days, but can cause long-lasting discomfort, bleeding and be excruciatingly painful. However, effective medical treatments are available.

Hemorrhoids (also called piles) can be divided into two kinds, internal and external. Internal hemorrhoids lie inside the anus or lower rectum. External hemorrhoids lie outside the anal opening. Both kinds can be present at the same time.

More than 75% of Americans have hemorrhoids at some point in their lives, typically after age 30. Pregnant women often develop hemorrhoids, but the condition usually clears up after childbirth. Men are more likely than women to suffer from hemorrhoids that require professional medical treatment.

Precisely why hemorrhoids develop is unknown. Researchers have identified a number of explanations for hemorrhoidal swelling, including the simple fact that people's upright posture places a lot of pressure...