Thomas P. Sokol, MD, FACS, FASCRS
Thomas P. Sokol, MD, FACS, FASCRS
Thomas P. Sokol, MD received his medical degree from the University of Health Sciences/The Chicago Medical School in 1980. He went on to his general surgical residency at Harbor/UCLA Medical Center and then to the Carle Clinic/ University of Illinois for Fellowship Training in Colon and Rectal Surgery.
In this Article
What causes hemorrhoids?
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It is not known why hemorrhoids enlarge. There are several theories about the cause, including inadequate intake of fiber, prolonged sitting on the toilet, and chronic straining to have a bowel movement (constipation). None of these theories has strong experimental support. Pregnancy is a clear cause of enlarged hemorrhoids though, again, the reason is not clear. Tumors in the pelvis also cause enlargement of hemorrhoids by pressing on veins draining upwards from the anal canal.
One theory proposes that it is the shearing (pulling) force of stool, particularly hard stool, passing through the anal canal that drags the hemorrhoidal cushions downward. Another theory suggests that with age or an aggravating condition, the supporting tissue that is responsible for anchoring the hemorrhoids to the underlying muscle of the anal canal deteriorates. With time, the hemorrhoidal tissue loses its mooring and slides down into the anal canal.
One physiological fact that is known about enlarged hemorrhoids that may be relevant to understanding why they form is that the pressure is elevated in the anal sphincter, the muscle that surrounds the anal canal and the hemorrhoids. The anal sphincter is the muscle that allows us to control our bowel movements. It is not known, however, if this elevated pressure precedes the development of enlarged hemorrhoids or is the result of the hemorrhoids. Perhaps during bowel movements, increased force is required to force stool through the tighter sphincter. The increased shearing force applied to the hemorrhoids by the passing stool may drag the hemorrhoids downward and enlarge them.
What are the symptoms of hemorrhoids?
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There are two types of nerves in the anal canal, visceral nerves (above the dentate line) and somatic nerves (below the dentate line). The somatic (skin) nerves are like the nerves of the skin and are capable of sensing pain. The visceral nerves are like the nerves of the intestines and do not sense pain, only pressure. Therefore, internal hemorrhoids, which are above the dentate line, usually are painless.
As the anal cushion of an internal hemorrhoid continues to enlarge, it bulges into the anal canal. It may even pull down a portion of the lining of the rectum above, lose its normal anchoring, and protrude from the anus. This condition is referred to as a prolapsing internal hemorrhoid. In the anal canal, the hemorrhoid is exposed to the trauma of passing stool, particularly hard stools associated with constipation. The trauma can cause bleeding and sometimes pain when stool passes. The rectal lining that has been pulled down secretes mucus and moistens the anus and the surrounding skin. Stool also can leak onto the anal skin. The presence of stool and constant moisture can lead to anal itchiness (pruritus ani), though itchiness is not a common symptom of hemorrhoids. The prolapsing hemorrhoid usually returns into the anal canal or rectum on its own or can be pushed back inside with a finger, but it prolapses again with the next bowel movement.
Less commonly, the hemorrhoid protrudes from the anus and cannot be pushed back inside, a condition referred to as incarceration of the hemorrhoid. Incarcerated hemorrhoids can have their supply of blood shut off by the squeezing pressure of the anal sphincter, and the blood vessels and cushions can die, a condition referred to as gangrene. Gangrene requires medical treatment.
For convenience in describing the severity of internal hemorrhoids, many physicians use a grading system:
In general, the symptoms of external hemorrhoids are different than the symptoms of internal hemorrhoids.
External hemorrhoids can be felt as bulges at the anus, but they usually cause few of the symptoms that are typical of internal hemorrhoids. This is perhaps, because they are low in the anal canal and have little effect on the function of the anus, particularly the anal sphincter. External hemorrhoids can cause problems, however, when blood clots inside them. This is referred to as thrombosis. Thrombosis of an external hemorrhoid causes an anal lump that is very painful (because the area is supplied by somatic nerves) and often requires medical attention. The thrombosed hemorrhoid may heal with scarring and leave a tag of skin protruding from the anus. Occasionally, the tag is large, which can make anal hygiene (cleaning) difficult or irritate the anus.
Medically Reviewed by a Doctor on 7/17/2014
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