Hemorrhoids are clumps of dilated (enlarged) blood vessels in the anus and lower rectum. The rectum is the last area of the large intestine before it exits to the anus. The anus is the end of the digestive tract where feces leaves the body.
Sometimes hemorrhoids swell when the veins enlarge and their walls become stretched, thin, and irritated by passing stool. Hemorrhoids are classified into two general categories