Inferior rectal veins
The hemorrhoidal plexus is a group of veins that surrounds the rectum. It has two parts, internal and external.
The inferior rectal veins are located in the external hemorrhoidal plexus. They are surrounded by loose connective tissue, so they do not get much support or constraint from the body. They are therefore less able to resist blood pressure. A varicosity of the inferior rectal veins — an abnormal swelling of these veins — is known as a hemorrhoid. The symptoms are swelling, irritation, and pain. They may protrude through the anus. Hemorrhoids often bleed, leaving bright red blood on the feces or toilet paper.
Risk factors for hemorrhoids include obesity, sitting for long periods, and a low fiber diet. These varicosities in the inferior rectal veins generally resolve on their own within one to two weeks.
Various medications are available that provide topical pain relief, but they do nothing for the cause of the varicosity. Doctors often prescribe high fiber diets and non-steroidal anti-inflammatory drugs. Surgery is generally reserved as a last-resort treatment option for those cases that do not heal with medication and diet changes. To avoid undue pressure on the inferior rectal veins, empty bowels soon after an urge.