When the veins around the anus or in the rectum are dilated (enlarged) or engorged with blood, the patient has hemorrhoids.
Experts aren’t sure what causes hemorrhoids to develop. Possible factors include:
- Pregnancy – they occur more commonly in pregnant women because, as the uterus enlarges, it presses on the vein in the colon, causing it to bulge.
- Aging – hemorrhoids are most common among adults aged 45-65. This does not mean, however, that young people and children do not get them.
- Diarrhea – especially when chronic.
- Chronic constipation – straining to move stool puts additional pressure on the blood vessels’ walls.
- Sitting – for long periods (especially on the toilet).
- Lifting – especially heavy objects repeatedly.
- Anal intercourse – which can cause hemorrhoids or worsen existing ones.
- Obesity – often dietary related, such as not following a high-fiber diet.
- Genetics (a family history of hemorrhoids) – some people inherit a tendency to develop hemorrhoids.
- Straining during a bowel movement
The exact cause of symptomatic hemorrhoids is unknown. A number of factors are believed to play a role, including irregular bowel habits (constipation or diarrhea), lack of exercise, nutritional factors (low-fiber diets), increased intra-abdominal pressure (prolonged straining, ascites, an intra-abdominal mass, or pregnancy), genetics, an absence of valves within the hemorrhoidal veins, and aging. Other factors believed to increase risk include obesity, prolonged sitting, a chronic cough, and pelvic floor dysfunction. Evidence for these associations, however, is poor.
During pregnancy, pressure from the fetus on the abdomen and hormonal changes cause the hemorrhoidal vessels to enlarge. The birth of the baby also leads to increased intra-abdominal pressures. Pregnant women rarely need surgical treatment, as symptoms usually resolve after delivery.
Hemorrhoid cushions are a part of normal human anatomy and become a pathological disease only when they experience abnormal changes. There are three main cushions present in the normal anal canal. These are located classically at left lateral, right anterior, and right posterior positions. They are composed of neither arteries nor veins, but blood vessels called sinusoids, connective tissue, and smooth muscle. Sinusoids do not have muscle tissue in their walls, as veins do. This set of blood vessels is known as the hemorrhoidal plexus.
Hemorrhoid cushions are important for continence. They contribute to 15–20% of anal closure pressure at rest and protect the internal and external anal sphincter muscles during the passage of stool. When a person bears down, the intra-abdominal pressure grows, and hemorrhoid cushions increase in size, helping maintain anal closure. Hemorrhoid symptoms are believed to result when these vascular structures slide downwards or when venous pressure is excessively increased. Increased internal and external anal sphincter pressure may also be involved in hemorrhoid symptoms. Two types of hemorrhoids occur: internals from the superior hemorrhoidal plexus and externals from the inferior hemorrhoidal plexus. The dentate line divides the two regions.
Hemorrhoids Causes and Risk Factors
Hemorrhoids form when the bundle of veins in the anus and lower rectum become enlarged and fall out of place (prolapse). Hemorrhoidal tissue, which consists of blood vessels, connective tissue, and some muscle, is actually a normal part of human anatomy. More accurately, it is the enlargement of hemorrhoids that causes discomfort.
Hemorrhoids are classified into two types: internal and external. Internal hemorrhoids develop inside the lower rectum and anus beneath the mucosa lining and are generally painless. External hemorrhoids show up as lumps around the anus and may cause severe pain. Treatment varies depending on the symptoms and diagnosis, and usually does not require surgery. In the U.S. it is estimated that 4.4% of adults suffer from hemorrhoids – the majority being 45-65 years old.
Activities that exert pressure on the vein clusters in the anus and lower rectum (also called anal cushions) are believed to cause enlarged hemorrhoids. Even the upright human posture is often blamed as a contributing factor.
- Irregular bowel movement. Constipation, excessive straining during a hard bowel, and sitting on the toilet for extended periods are all associated with symptomatic hemorrhoids. These activities can disrupt blood flow to anal cushions, and lead to bulging and prolapse of internal hemorrhoids, or blood clotting in external hemorrhoids. Chronic diarrhea and overuse of laxatives and enemas may also exacerbate these symptoms.
- Pregnancy. Symptomatic hemorrhoids are common during pregnancy because the expanding uterus pushes against the anal cushions. This condition is temporary and usually resolves itself after birth.
- Age. As the body ages, the tissues supporting hemorrhoids can weaken, allowing prolapse.
Hemorrhoids can be passed on genetically from parent to child, so if your parents had hemorrhoids, you’re more likely to get them. Consistent heavy lifting, being obese, or having other constant strain on your body can increase your risk of hemorrhoids.
Standing too much without taking a break to sit can cause hemorrhoids to develop. Consistent anal sexual intercourse and diarrhea can also increase your risk of hemorrhoids.
You’re also more likely to develop hemorrhoids if you’re pregnant. When the uterus enlarges, it presses on the vein in the colon, causing it to bulge.