出典(authority):フリー百科事典『ウィキペディア(Wikipedia)』「2013/06/05 06:49:53」(JST)
Hemorrhoids | |
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Classification and external resources | |
Diagram demonstrating the anal anatomy of both internal and external hemorrhoids |
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ICD-10 | I84 |
ICD-9 | 455 |
DiseasesDB | 10036 |
MedlinePlus | 000292 |
eMedicine | med/2821 emerg/242 |
MeSH | D006484 |
Hemorrhoids (US English) or haemorrhoids UK /ˈhɛmərɔɪdz/, are vascular structures in the anal canal which help with stool control.[1][2] They become pathological or piles[3] when swollen or inflamed. In their physiological state, they act as a cushion composed of arterio-venous channels and connective tissue.
The symptoms of pathological hemorrhoids depend on the type present. Internal hemorrhoids usually present with painless rectal bleeding while external hemorrhoids may produce few symptoms or if thrombosed significant pain and swelling in the area of the anus. Many people incorrectly refer to any symptom occurring around the anal-rectal area as "hemorrhoids" and serious causes of the symptoms should be ruled out.[4] While the exact cause of hemorrhoids remains unknown, a number of factors which increase intra-abdominal pressure, in particular constipation, are believed to play a role in their development.
Initial treatment for mild to moderate disease consists of increasing fiber intake, oral fluids to maintain hydration, NSAIDs to help with the pain, and rest. A number of minor procedures may be performed if symptoms are severe or do not improve with conservative management. Surgery is reserved for those who fail to improve following these measures. Up to half of people may experience problems with hemorrhoids at some point in their life. Outcomes are usually good.
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Internal and external hemorrhoids may present differently; however, many people may have a combination of the two.[2] Bleeding significant enough to cause anemia is rare,[5] and life threatening bleeding is even more uncommon.[6] Many people feel embarrassed when facing the problem[5] and frequently seek medical care only when the case is advanced.[2]
If not thrombosed, external hemorrhoids may cause few problems.[7] However, when thrombosed, hemorrhoids may be very painful.[2][3] Nevertheless this pain typically resolves in 2 – 3 days.[5] The swelling however may take a few weeks to disappear.[5] A skin tag may remain after healing.[2] If hemorrhoids are large and cause issues with hygiene, they may produce irritation of the surrounding skin and thus itchiness around the anus.[7]
Internal hemorrhoids usually present with painless, bright red, rectal bleeding during or following a bowel movement.[2] The blood typically covers the stool, a condition known as hematochezia, is on the toilet paper, or drips into the toilet bowl.[2] The stool itself is usually normally coloured.[2] Other symptoms may include mucous discharge, a perianal mass if they prolapse through the anus, itchiness, and fecal incontinence.[6][8] Internal hemorrhoids are usually only painful if they become thrombosed or necrotic.[2]
The exact cause of symptomatic hemorrhoids is unknown.[9] A number of factors are believed to play a role including: irregular bowel habits (constipation or diarrhea), a lack of exercise, nutritional factors (low-fiber diets), increased intra-abdominal pressure (prolonged straining, ascitis, an intra-abdominal mass, or pregnancy), genetics, an absence of valves within the hemorrhoidal veins, and aging.[3][5] Other factors that are believed to increase the risk include obesity, prolonged sitting,[2] a chronic cough and pelvic floor dysfunction.[4] Evidence for these associations, however, is poor.[4]
During pregnancy, pressure from the fetus on the abdomen and hormonal changes cause the hemorrhoidal vessels to enlarge. Delivery also leads to increased intra-abdominal pressures.[10] Pregnant women rarely need surgical treatment, as symptoms usually resolve after delivery.[3]
Hemorrhoid cushions are a part of normal human anatomy and become a pathological disease only when they experience abnormal changes.[2] There are three main cushions present in the normal anal canal.[3] These are located classically at left lateral, right anterior, and right posterior positions.[5] They are composed of neither arteries nor veins but blood vessels called sinusoids, connective tissue and smooth muscle.[4] Sinusoids do not have muscle tissue in their walls, as veins do.[2] This set of blood vessels is known as the hemorrhoidal plexus.[4]
Hemorrhoid cushions are important for continence. They contribute to 15–20% of anal closure pressure at rest and protect the anal sphincter muscles during the passage of stool.[2] When a person bears down, the intra-abdominal pressure grows, and hemorrhoid cushions increase in size helping to maintain the anus closed.[5] It is believed that hemorrhoid symptoms result when these vascular structures slide downwards or when venous pressure is excessively increased.[6] Increased anal sphincter pressure may also be involved in hemorrhoid symptoms.[5] Two types of hemorrhoids occur: internals from the superior hemorrhoidal plexus and externals from the inferior hemorrhoidal plexus.[5] The dentate line divides the two regions.[5]
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3 | ||
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Hemorrhoids are typically diagnosed by physical examination.[11] A visual examination of the anus and surrounding area may diagnose external or prolapsed hemorrhoids.[2] A rectal exam may be performed to detect possible rectal tumors, polyps, an enlarged prostate, or abscesses.[2] This examination may not be possible without appropriate sedation due to pain, although most internal hemorrhoids are not associated with pain.[3] Visual confirmation of internal hemorrhoids may require anoscopy, a hollow tube device with a light attached at one end.[5] There are two types of hemorrhoids: external and internal. These are differentiated by their position with respect to the dentate line.[3] Some persons may concurrently have symptomatic versions of both.[5] If pain is present the condition is more likely to be an anal fissure or an external hemorrhoid rather than an internal hemorrhoid.[5]
Internal hemorrhoids are those that originate above the dentate line.[7] They are covered by columnar epithelium which lacks pain receptors.[4] They were classified in 1985 into four grades based on the degree of prolapse.[3][4]
External hemorrhoids are those that occur below the dentate or pectinate line.[7] They are covered proximately by anoderm and distally by skin, both of which are sensitive to pain and temperature.[4]
Many anorectal problems, including fissures, fistulae, abscesses, colorectal cancer, rectal varices and itching have similar symptoms and may be incorrectly referred to as hemorrhoids.[3] Rectal bleeding may also occur due to colorectal cancer, colitis including inflammatory bowel disease, diverticular disease, and angiodysplasia.[11] If anemia is present, other potential causes should be considered.[5]
Other conditions that produce an anal mass include: skin tags, anal warts, rectal prolapse, polyps and enlarged anal papillae.[5] Anorectal varices due to increased portal hypertension (blood pressure in the portal venous system) may present similar to hemorrhoids but are a different condition.[5]
A number of preventative measures are recommended including avoiding straining while attempting to defecate, avoiding constipation and diarrhea either by eating a high fiber diet and drinking plenty of fluid or taking fiber supplements, and getting sufficient exercise.[5][12] Spending less time attempting to defecate, avoiding reading while on the toilet,[3] as well as losing weight for overweight persons and avoiding heavy lifting are also recommended.[13]
Conservative treatment typically consists of nutrition rich in dietary fiber, uptake of oral fluids to maintain hydration, non-steroidal anti-inflammatory drugs (NSAID)s, sitz baths, and rest.[3] Increased fiber intake has been shown to improve outcomes,[14] and may be achieved by dietary alterations or the consumption of fiber supplements.[3][14] Evidence for benefits from sitz baths during any point in treatment however is lacking.[15] If they are used they should be limited to 15 minutes at a time.[4]
While many topical agents and suppositories are available for the treatment of hemorrhoids, there is little evidence to support their use.[3] Steroid containing agents should not be used for more than 14 days as they may cause thinning of the skin.[3] Most agents include a combination of active ingredients.[4] These may include: a barrier cream such as petroleum jelly or zinc oxide, an analgesic agent such as lidocaine, and a vasoconstrictor such as epinephrine.[4] Flavonoids are of questionable benefit with potential side effects.[4][16] Symptoms usually resolve following pregnancy; thus active treatment is often delayed until after delivery.[17]
A number of office based procedures may be performed. While generally safe, rare serious side effects such as perianal sepsis may occur.[11]
A number of surgical techniques may be used if conservative management and simple procedures fail.[11] All surgical treatments are associated with some degree of complications including bleeding, infection, anal strictures and urinary retention, due to the close proximity of the rectum to the nerves that supply the bladder.[3] There may also be a small risk of fecal incontinence, particularly of liquid,[4][19] with rates reported between 0% and 28%.[20] Mucosal ectropion is another condition which may occur after hemorrhoidectomy (often together with anal stenosis).[21] This is where the anal mucosa becomes everted from the anus, similar to a very mild form of rectal prolapse.[21]
It is difficult to determine how common hemorrhoids are as many people with the condition do not see a healthcare provider.[6][9] However, it is believed that symptomatic hemorrhoids affect at least 50% of the US population at some time during their lives and around ~5% of the population is affected at any given time.[3] Both sexes experience approximately the same incidence of the condition[3] with rates peaking between 45 and 65 years.[5] They are more common in Caucasians[25] and those of higher socioeconomic status.[4] Long term outcomes are generally good, although some people may have recurrent symptomatic episodes.[6] Only a small proportion of persons end up needing surgery.[4]
The first known mention of this affliction is from a 1700 BC Egyptian papyrus, which advises: “… Thou shouldest give a recipe, an ointment of great protection; Acacia leaves, ground, titurated and cooked together. Smear a strip of fine linen there -with and place in the anus, that he recovers immediately."[26] In 460 BC, the Hippocratic corpus discusses a treatment similar to modern rubber band ligation: “And hemorrhoids in like manner you may treat by transfixing them with a needle and tying them with very thick and woolen thread, for application, and do not forment until they drop off, and always leave one behind; and when the patient recovers, let him be put on a course of Hellebore.”[26] Hemorrhoids may have been described in the Bible.[5][27]
Celsus (25 BC – AD 14) described ligation and excision procedures, and discussed the possible complications.[28] Galen advocated severing the connection of the arteries to veins, claiming that it reduced both pain and the spread of gangrene.[28] The Susruta Samhita, (4th – 5th century AD), similar to the words of Hippocrates, but emphasizes wound cleanliness.[26] In the 13th century, European surgeons such as Lanfranc of Milan, Guy de Chauliac, Henri de Mondeville and John of Ardene made great progress and development of the surgical techniques.[28]
The first use of the word "hemorrhoid" in English occurs in 1398, derived from the Old French "emorroides", from Latin "hæmorrhoida -ae",[29] in turn from the Greek "αἱμορροΐς" (haimorrhois), "liable to discharge blood", from "αἷμα" (haima), "blood"[30] + "ῥόος" (rhoos), "stream, flow, current",[31] itself from "ῥέω" (rheo), "to flow, to stream".[32]
Hall-of-Fame baseball player George Brett was removed from a game in the 1980 World Series due to hemorrhoid pain. After undergoing minor surgery, Brett returned to play in the next game, quipping "...my problems are all behind me."[33] Brett underwent further hemorrhoid surgery the following spring.[34] Conservative political commentator Glenn Beck underwent surgery for hemorrhoids, subsequently describing his unpleasant experience in a widely viewed 2008 YouTube video.[35]
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