Hemorrhoids (Piles)

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What is the definition of a hemorrhoid?

Hemorrhoids (Piles) are blood vessels located in the smooth muscles of the walls of the rectum and anus. They are a normal part of the anatomy and are located at the junction where small arteries merge into veins. They are cushioned by smooth muscles and connective tissue and are classified by where they are located in relationship to the pectinate line, the dividing point between the upper 2/3 and lower 1/3 of the anus. This is an important anatomic distinction because of the type of cells that line the hemorrhoid, and the nerves that provide sensation.

Internal hemorrhoids are located above the pectinate line and are covered with cells that are the same as those that line the rest of the intestines. External hemorrhoids arise below the line and are covered with cells that resemble skin.

Hemorrhoids become an issue only when they begin to swell, causing itching, pain and/or bleeding.

Hemorrhoids Pictures Slideshow: Causes, Symptoms, and Treatment

What causes hemorrhoids?

While the presence of hemorrhoids is a reflection of the normal anatomy, most people and care professionals refer to hemorrhoids as an abnormal finding because they only present when they swell and cause problems.

Hemorrhoid swelling occurs when there is an increase in the pressure in the small vessels that make up the hemorrhoid causing them to swell and engorge with blood. This causes them to increase in size leading to symptoms. Increased pressure may be caused by a variety of factors:

  • Low fiber diet and smaller caliber stool causes a person to strain when having a bowel movement, increasing the pressure within the blood vessels.
  • Pregnancy is associated with hemorrhoid swelling and is likely due to increased pressure of the enlarged uterus on the rectum and anus. In addition, hormonal changes with pregnancy may weaken the muscles that support the rectum and anus.
  • Prolonged sitting on the toilet may increase pressure within the hemorrhoid blood vessels
  • Obesity
  • Diarrhea, both acute and chronic
  • Colon cancer
  • Previous rectal surgery
  • Spinal cord injury and lack of erect posture
Medically Reviewed by a Doctor on 2/5/2015

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Rectal Bleeding Symptoms and Causes

Blood in the stool can be bright red, maroon in color, black and tarry, or occult (not visible to the naked eye). Examples of causes of blood in the stool are:

  • Hemorrhoids
  • Cancer
  • Anal fissures
  • Crohn's disease
  • Ulcerative colitis
  • Anal cancer

Blood in the stool should be evaluated by a health-care professional.