Hemorrhoids are swollen blood vessels that are found in and around the anus and lower rectum. They can be internal, which means inside the anus. Or, they may be external, which means they are found outside the anus.
The blood vessels around the anus swell and may bleed or cause other symptoms. The exact cause of hemorrhoids is not always clear.
Hemorrhoids are related to dilated blood vessels, but the exact cause is not always clear. Some types of hemorrhoids run in families. Other factors that increase your risk for hemorrhoids include: