1 The concept of hemorrhoids
In the 20th century, especially after the 1970s, with the advancement of science and technology, people’s understanding of hemorrhoids has made a leap, and a new concept has been formed, namely: hemorrhoids are the lip-shaped fleshy or anal cushions at the lower end of the rectum. It is a normal structure that everyone has; the anal cushion is arranged in the right anterior, right posterior, and left three leaves, and has nothing to do with the superior rectal artery branch. They are like the tricuspid valve of the heart, helping the sphincter to maintain the normal closure of the anal canal; the pathological hypertrophy of the anal cushion is called hemorrhoids. The principle of treatment of hemorrhoids is mainly based on symptoms. For asymptomatic hemorrhoids, even if the next wall is large, it is not necessarily an indication for treatment. On the contrary, when hemorrhoids are small but are at risk of serious complications, they must be treated. The above concept was first proposed by Thomson in 1975, and was supported by some famous scholars such as Alexander-Williams (1982), Bernstein (1983) and Melzier (1984). In 1983, it was unanimously confirmed at the 9th International Hemorrhoids Symposium held in Cologne, Germany. The new definition of hemorrhoids has been widely adopted in recent foreign monographs on anorectology.
2 Embryology of hemorrhoids
Anal cushion is also called haemorrhoidal zone or zona columaris. Embryologists call this zone a cloacogenic zone or transitional zone or invaginational zone. zone). Because this area is located at the junction of the anal canal and the intestine, the embryonic primordia of epithelium, glands, blood vessels and muscles are intertwined here, so it has its morphological characteristics and is an important critical zone.
2.1 Rectal descent and anorectal intussusception. In the early embryonic stage, the end of the original rectum (the hindgut) is located in the abdominal cavity, and it falls below the pelvic diaphragm at 3 months of viviparous period to contact the original anal cavity; then the original anal cavity is invaded upwards into the lower end of the hindgut . At the intussusception, the posterior intestinal mucosa folds into a double layer, the inner side of which is the anal canal epithelium, and the three gradually fuse and thicken, forming a ring-shaped spongy tissue band, that is, anal cushion. Due to the contraction of the internal sphincter, the anal cushion is divided into three parts on the right front, right back and left side by the Y-shaped groove. This is usually called the "maternal hemorrhoid" and its "prone site".
As early as 1954, Last discovered that the internal sphincter of the hindgut and the external sphincter of the original anus were arranged up and down during the viviparous period, and changed to the internal and external arrangement with the development of the human embryo; therefore, early scholars once referred to the former as the upper sphincter. , The latter is the lower sphincter. Stephens also pointed out in 1963 that the anal cushion epithelium (ie, hemorrhoid epithelium) at the end of the hindgut is not a colonic intestinal type, but a squamous epithelium from the original anus. The above findings can be used as evidence for anal intussusception.
2.2 Anal membrane rupture and ATZ epithelial formation Data show that the hemorrhoidal epithelium is ATZ epithelium. The occurrence of ATZ is related to the location of the anal membrane rupture. The anal membrane is the diaphragm between the original rectum and the original anus. The upper part of the anal membrane is the endoderm and the lower part is the ectoderm. In the past, from the embryology point of view, it has been believed that the anal membrane ruptures at 8 weeks of pregnancy, and the ectoderm squamous epithelium crawls up to form a transitional epithelial zone, the so-called ATZ. However, there are different opinions about the location of the anal membrane rupture. According to Nobles (1984) observation; the shape of the anal membrane provided to adults in the early embryo is only approximate, because with the appearance and migration of the sphincter, that is, the external sphincter grows upward and the internal sphincter grows upward. Move down, the anal membrane attachment will change accordingly. The anal membrane ruptures before the anal flap (or tooth line) appears. The first appearance of the anal flap was about 30mm in the human embryo. At the 35mm stage of the human embryo, the upper boundary of the combi membrane reaches the junction with the rectal mucosa, and there is an overlapping area of squamous epithelium and columnar epithelium, which gradually expands to an adult about 15mm wide. Therefore, the anorectal junction does not have a clear dividing line, but an irregular area of squamous and columnar epithelium. The observation results of modern application of optics and electron microscope show that the ultrastructure of ATZ epithelium is similar to that of cloacal epithelium, thus confirming that the ATZ above the plane of the anal flap (or dentinal line) (anal cushion) represents the boundary between endoderm and ectoderm, that is, anal The attachment of the membrane is also the belt that connects the anal canal to the rectum. Fenger used alcian blue staining method to observe: the rectal columnar epithelium rich in mucin is stained blue, while the anal squamous epithelium does not contain mucin. The transitional epithelium of the anal cushion contains less mucin, so it is dyed light blue, which can be distinguished from the above two types of epithelium.
In summary, from the genetic point of view, hemorrhoids are developed from anorectal intussusception, which is a normal structure of human anatomy.
3 Hemorrhoid epithelium
The mucous membrane of the anal cushion is purple-red, and it turns pink at the upper border with the rectum. Histologically, the anal cushion epithelium is a transitional epithelium between a single layer of columnar epithelium and stratified squamous epithelium. The cells are columnar, cubic or low-cubic, among which there are still single layer of columnar or stratified squamous cells. Small island. Histochemical methods proved that there is a small amount of mucus on the surface of columnar cells or in the more typical goblet cells. Most of the squamous epithelium is undifferentiated. In about 31.9% of the population, the differentiated type is normal squamous epithelium, and its distribution area is at least 2mm.
In 1982, Fenger et al. found that there are endocrine argyrophilic cells or EC cells in the anal cushion epithelium. These cells seem to be connected with its mucosal nerve plexus. The pudendal nerve is cut off. The ribonucleic acid contained in argyrophilic cells is significantly reduced. Cells may initiate afferent excitement related to anal six atresia.
In 1985, Taniguchi Rizhao et al. used the enzyme antibody method (PAP method) to stain the anal cushion excision specimens for IgA tissue staining, and found that there were moderate to highly scattered spindle-shaped cells in the anal cushion epithelium. However, in the rectal tissue above the anal cushion, darkly stained cells are rarely seen. It is inferred from this that if inflammation occurs in the anal canal area, the secretion of IgA in the epithelium of the anal cushion will increase. Even after internal hemorrhoids are removed, the secretion of IgA is considered to be part of the prevention of infection.
The sensory nerve endings in the epithelium of the anal cushion are extremely abundant. Krause’s final ball is more numerous with Glogi-Mazzoni bodies and Pacinian bodies; the former is sensitive to temperature, while the latter is responsible for changes in tension and pressure. The number of Meissner corpuscles is relatively rare, with slight touch. In addition, there are somatic sensory nerves that extend across the dentinal line to the lower edge of the anal cushion. The distribution of nerves in the anal cushion is different from that of the skin, but has obvious similarities with the nerve branches of the lips. These nerves are important sensory devices in the anal reflex, and have a fine discrimination ability to the nature of rectal contents. This discrimination may be the function of internal rectal pressure. The anal cushion is closed at rest, and the rectal contents will not interact with the receptors. Contact, when hard stools, loose stools or gas inflates the rectum, it reflexively causes a decrease in intraanal pressure (internal sphincter relaxation). At this time, different contents cause different pressures to contact the anal cushion and feel the epithelium. Distinguish and trigger an attempt to reflect. Therefore, although the area of the receptors in the anal cushion area is small, it can act as an alarm when the stool is close to the anus, so it has a certain protective function.
It is worth noting that the ATZ epithelium in the anal cushion area is a highly specialized sensory nerve terminal tissue zone, which is very sensitive and is the sensory center that induces defecation, also known as the trigger zone. When feces are sent from the rectum to the anal canal, the ATZ is stimulated to reach the brain through the sensory nerves to produce a sense of defecation. If this area is completely destroyed, the sensation of bowel movement disappears and the stool in the rectum will become stagnant. According to the physiological characteristics of the above-mentioned ATZ, it can explain the causes of some abnormal bowel movements in the clinic. For example, prolapsed anal diseases (rectal prolapse, polyps, etc.), the prolapse is embedded in the anus or prolapses outside the anus during defecation; after the stool is discharged, the prolapse remains in the original state, which stimulates the ATZ epithelium of the anal pad and produces a defecation sensation. Misunderstanding the abnormal bowel sensation for the residual feces and working hard, the prolapsed matter is more prolapsed, causing a vicious circle. This is why patients with rectal cancer in the lower rectum often have abnormal bowel movements.
In summary, the anal cushion epithelium has certain immune and endocrine functions, fine discrimination, and a variety of chemical and mechanical receptors, which can trigger protective anal reflexes. It is very important to maintain normal bowel movements.
4.1 The branch pattern of the suprahemorrhoidal artery has nothing to do with the location of the mother hemorrhoids. In 1919, Miles proposed that the suprahemorrhoidal artery was divided into two left and right branches, and the right branch was divided into two anterior and posterior branches and distributed in the hemorrhoid area together with the left lateral branch, and emphasized the introduction The branching pattern is related to the causes of the three female hemorrhoids. However, the research reports of modern scholars are not consistent with Miles' diagnosis. Michels (1965) divided the suprahemorrhoidal artery into 4 types, and none of the types described by Miles were found. Foster (1984) and Senkeye (1984) pointed out that the left and right branches of the suprahemorrhoidal artery can be divided into anterior and posterior branches or most of the secondary branches, without a fixed pattern. The author (1986) once dissected and observed 76 cadavers, and found that there were 3 branches of right anterior, right posterior and left lateral as described by Miles. Only 5 cases were found, accounting for 6.6%. Therefore, Miles used the branch pattern of the superior rectal artery to explain the prevalence of internal hemorrhoids, which lacked anatomical support. What's more, the blood vessels are mutated, and the positions of the right front, right back, and left side of the anal cushion are indeterminate. There is no logical connection between the two. It has been confirmed that the arteries of the anal cushion mainly come from the inferior rectal artery (middle hemorrhoidal artery) and anal artery (inferior hemorrhoidal artery), and the superior rectal artery generally does not participate. The three-part arrangement of the anal cushion has nothing to do with the branching pattern of the superior rectal artery.
The traditional concept also believes that the density of microvessels in the hemorrhoid area is different. Because the blood vessels distributed in the right front, right back and left side are particularly dense, mother hemorrhoids often occur here. For this reason, Haruo Miyazaki (1976) and the author (1986) observed the microvessel density in the anal cushion through arteriography and found that the microvessels of the middle hemorrhoidal artery and the anal artery converge here from six directions, and the distribution is uniform throughout the week without bias. Nothing was found that the microvessels on the right front, right back, and left were particularly dense compared to other places. If the formation of hemorrhoids is related to microvessels, hemorrhoids cannot be limited to three specific locations. Therefore, the distribution pattern of arterial capillaries in the anal cushion has nothing to do with the prone site of hemorrhoids.
4.2 Non-pathological phenomena of hemorrhoidal vein expansion As early as the 18th century, Sappey, Dyret, Waldeyer and Thomson et al. confirmed that from newborn babies to healthy adults, the phenomenon of hemorrhoidal vein expansion is constant, which is different from the great saphenous vein. Or esophageal varicose veins without any pathological damage to the vein wall, which is a normal physiological expansion. In 1982, French scholar Saint-Pierre discovered that female internal hemorrhoids have estrogen receptors. When the level of estrogen receptors increases during pregnancy and menstrual cycles, stimulation of these chemical receptors can reflexively cause vein dilation, which is also a physiological phenomenon.
The submucosal veins of the anal cushion (internal hemorrhoid plexus) are the same as the adjacent pudendal plexus, bladder plexus, and uterine vaginal plexus. They are all normal patterns of pelvic organ veins. Under normal circumstances, there is extensive communication between the internal hemorrhoidal venous plexus and the portal vein and systemic vein in the rectum. Portal vein blood can be shunted to the systemic circulation (internal iliac vein) via the inter-hemorrhoid communicating vein and hemorrhoidal reproductive vein. The rectum contracts during defecation. The shunt phenomenon is more pronounced. In 1985, Shafik found through hemorrhoid plexography that the hemorrhoidal reproductive vein has the function of a venous valve, which only allows blood from the hemorrhoidal venous plexus to flow to the prostate venous plexus or vaginal venous plexus (systemic circulation), while systemic blood cannot flow to the portal vein system. Therefore, portal hypertension is not directly related to hemorrhoids. According to statistics, the incidence of hemorrhoids in patients with portal hypertension is not high. Jacobs et al. (1980) investigated 188 patients with portal hypertension, 52 patients with hemorrhoids, accounting for 28%. The incidence of hemorrhoids in the average person is as high as 50% to 80%. Other scholars such as Hunt, Orloff, etc. have the same report, so the above conclusions have also been confirmed clinically. The traditional concept of hemorrhoids caused by blood stasis and varicose plexus has been abandoned. Since the internal hemorrhoid plexus is part of the rectal venous plexus, if the venous plexus is stasis, the latter has the effect of absorbing excessive congestion and will not cause varicose veins; if varicose veins occur, it will also involve the entire rectal venous plexus and will not be limited to internal hemorrhoids Clump. Therefore, although the venous plexus of the anal cushion and hemorrhoids are closely related, they are not the main cause of disease.
4.3 anastomosis arteriovenosa is the blood volume regulator of the anal cushion. In 1962, Stelzner et al. found that there was an arteriovenous anastomosis in the submucosa of the anal cushion in serial tissue sections. In 1963, Staubesand et al. used X-ray angiography, and Thomson used latex injection in 1975, which successively confirmed the existence of this special blood vessel. Thomson called this type of blood vessel "sinusoidal vein." The silk ball-like structure of the arteriovenous anastomosis is a unique blood vessel pattern in the anal cushion.
Arteriovenous anastomosis refers to a direct anastomosis tube between small arteries and small veins. Blood can flow from arteries to veins without passing through capillaries. Such blood vessels can go straight or be spherical or tortuous. The structure of the tube wall is very special: endothelial cells directly connect with deformed smooth muscle cells, and there are abundant nerve fibers in the outer membrane. Under normal circumstances, the opening or closing of the arteriovenous anastomosis in the anal cushion is alternately opened and opened every minute. ～12 times, some are open for several days or closed for several days. Because the anastomotic tube can be freely opened, it has a major effect on the temperature and blood volume of the anal cushion area. Because the arterial blood flows directly into the veins, the venous blood of the anal cushion venous plexus can be arterialized, and even rhythmic pulsation occurs in the vein. Thulesins et al.’s experimental studies on blood gas analysis and thermoconeuctibility of hemorrhoid blood have strongly confirmed the existence of such anastomotic tubes in the anal cushion, and gave reasonable answers to why hemorrhoid blood is bright red (arterial blood) .
Arteriovenous anastomosis is a good blood volume regulator for the anal cushion. The amount of blood supplied to the anal cushion is closely related to its functional state and the stimulation of the internal and external environment. Under normal circumstances, the blood flow of the anal pad anastomosis tube accounts for 20% of the total rectal blood volume, even up to 50%. Due to low levels of sex hormones in children, the anastomotic tube is not fully developed until puberty, so children rarely experience anal hypertrophy. During pregnancy, the level of estrogen increases, the anastomotic tube becomes thicker, and the blood flow increases, so the incidence of hemorrhoids in pregnant women is high.
The contraction and relaxation of the smooth muscle of the arteriovenous anastomosis tube are innervated by sympathetic nerve fibers and regulated by vasoactive substances in the blood. Active substances can be divided into two categories, namely blood contractile hormones (norepinephrine, epinephrine, serotonin, angiotensin, etc.) and vasodilators (histamine, vasomotor, vasodilator, nucleoside) Acid and lactic acid etc.). The former is systemic and its concentration changes little, while the latter is produced by local tissues. When the anal cushion is stimulated by some unfavorable factor, sympathetic nerves are stimulated. At first, the secretion of crude amine substance increases, causing anastomotic spasm, tissue ischemia and hypoxia; then the anal cushion tissue is stimulated by hypoxia to release histamine, resulting in localized tissue Amine action, anastomotic tube dilation, blood stasis, tissue edema, blood clot formation, severe cases can develop into local necrosis, erosion and bleeding. Therefore, dysregulation of arteriovenous anastomosis may be one of the factors of hemorrhoids.
5 Fixation of hemorrhoids
There are two types of submucosal connective tissues in the anal cushion, namely supportive connective tissue and stable connective tissue; the former refers to the intrinsic components of the submucosa, and the latter refers to the fibers that join the longitudinal muscles through the internal sphincter and enter the anal cushion, and the inner surface of the internal sphincter , Forming a layer of fibromuscular tissue with a mixture of collagen fibers, elastic fibers and smooth muscle fibers. Treitz first described this fiber in 1853, so it was called Treitz muscle. Fine-Lswes (1940) is called the submucosal muscle.
The Treitz muscle is essentially the extension and continuity of the levator ani tendon fibers, and the anal cushion is suspended from the pelvic wall by the funnel-shaped pelvic diaphragm. Jit (1974) confirmed that the anus levator is a mixed muscle, and the fiber that penetrates into the anal cushion is not striated muscle but smooth muscle, which wraps around the hemorrhoidal venous plexus in a network shape; when it contracts, the muscle network tightens to restrain the hemorrhoidal veins and anal cushion Shrink; when flaccid; the venous plexus is passively enlarged, and the anal cushion expands accordingly to maintain anal self-control.
The thickness of Treitz muscle is about 1 to 3mm, which increases with age and becomes stable after the age of 20. The ratio of Treitz muscle thickness to internal sphincter thickness is 1:4 for newborns, 1:2 for adults, and 1:1.5 for the elderly. The young Treitz muscle fibers are densely arranged, parallel to each other, with fine structure and more elastic fibers. By about 30 years of age, Treitz muscle fibers begin to degenerate, appear broken, twisted and loose, and elastic fibers decrease. The observation of Thomson (1975) confirmed that the distribution of this fibromuscular tissue in the anal cushion is mainly in the form of a network structure wrapped around the hemorrhoidal venous plexus to form a supportive framework that fixes the anal cushion on the internal sphincter. The function is to prevent the anal cushion from slipping off. Therefore, Kohlvansch (1854) called Treitz muscle as a sustentator tuniae mucosae. The support device wrapped around the hemorrhoid blood vessels in young people is stronger and tougher, and degeneration occurs in old age, the support device is loose, and the anal cushion tends to protrude from the anal cavity.
As mentioned above, the Treitz muscle is the network and support structure of the anal cushion. It has the function of retracting the anal cushion upward after defecation. If the Treitz muscle ruptures and the supporting tissues relax, the anal cushion can appear retraction obstacles and move down from its original position fixed to the internal sphincter. There are many factors that cause the anal cushion to move down. In addition to the genetic factors of congenital Treitz muscle dysplasia, such as constipation, anger, chronic diarrhea, poor bowel habits and sphincter dysmotility, all of which can increase the verticality of the anal cushion. The pressure causes Treitz muscles to overstretch and break, causing the anal cushion to move down. For another example, the anal pad will experience congestive hypertrophy when the arteriovenous anastomosis occurs in the anal cushion, and when the blood perfusion increases. The normal Treitz muscle network venous plexus has a restrictive effect on the volume of the anal cushion. When the congestion continues to increase, the volume of the anal cushion will continue to increase, resulting in the extension, hypertrophy and rupture of the Treitz muscle. Once the anal cushion loses the support of the muscle layer, intermittent prolapse can occur over time, and then it will develop into continuous prolapse. It must be pointed out that the age factor cannot be ignored. It has been clarified in the 1960s that the fibers and cells of the anal cushion support tissue gradually degenerate with age. This is because the changes in glia-forming enzymes due to age affect the synthesis of glia and degrade natural glia. In 1984, Hass et al. pointed out that Treitz muscle degeneration began approximately at the age of 18-20, and it aggravated with age, becoming distorted and loosened, naturally broken, and anal cushions moved down, so the incidence of hemorrhoids increased greatly.
6 Hemorrhoids play a role in maintaining anal self-control
Marti (1989) pointed out that a normal anal cushion is like a heart tricuspid valve. Its main function is to assist the sphincter to ensure the normal closure of the anus and maintain fecal self-control.
The cushion-like structure is a common feature of various cavities lined by mucous membranes in the body, and it helps to close the cavities.For example, the rosette of the mucous membrane of the gastric cardia is similar to the structure of the anal cushion. It participates in the one-way valve of the cardia and prevents the reflux of gastric juice to the esophagus. Other pyloric valve, ileocecal valve, appendix valve, etc. all have functions similar to anal cushion. Alexander-Williams believes that the anal cushion is very similar to the lips; the lips have different shapes, such as thin, convex, wet, congested, etc., and the anal cushion can also have different shapes and should not be called a disease. The three-lobed arrangement of the anal cushion is the most ideal valve device to adapt to the expansion or contraction of the anal cavity. Because there are abundant arteriovenous anastomosis and Treitz muscles in the anal cushion, the structure resembles the cavernous body of the penis, so Stelzner calls the anal cushion corpus cavernosum recti. A large amount of blood can be contained in the cavernous body, so that the blood supply of the anal cushion greatly exceeds the needs of metabolism. Therefore, it can be proved that the anal cushion has the characteristics of erectile tissue and is necessary for participating in anal self-control.
The size of the anal cushion is related to the opening or closing of the arteriovenous anastomosis tube and the amount of blood supply in the anal cushion. Work, defecation and changes in body position can all affect the increase or decrease of the anal cushion. If the anal cushion is turned from the supine position to the upright position, the intravascular pressure of the anal cushion can rise rapidly from 22.5～24.5kpa (230～250mmH2O) to 58.8～73.5kPa (600～750mmH2O). It can be said that the size of the anal cushion changes every day or every hour. After defecation, the anal cushion may fall out or become congested, but after a period of rest, the volume of the anal cushion is not large after a rectal examination. Patients often complain that "hemorrhoids" are sometimes large and sometimes not large; sometimes "hemorrhoids attacks" last for several days or weeks. Therefore, the traditional classification of internal hemorrhoids of stage I, II, III or IV is of little clinical and scientific significance.
Under normal circumstances, the resting pressure of the anal canal is the sum of the vascular pressure of the anal cushion and the tension of the sphincter. The two are complementary: when the sphincter pressure decreases, the anal cushion expands; when the sphincter pressure increases, the anal cushion is compressed. When the sphincter is in a relaxed state, blood enters the venous space of the anal cushion, the anal cushion expands, assists the resting pressure of the anal canal, and maintains the anus closed. Raz (1972) had done a test that blocked the blood of the spongy erectile tissue under the mucous membrane of the female urethra (clamping the internal iliac artery), and found that the pressure in the urethra decreased rapidly by 35%, which indirectly proved that the internal anal canal The vascular components of the anal cushion are important in helping the sphincter maintain anal self-control. According to reports in the literature, patients with prolapsed hemorrhoids or hemorrhoidectomy have different degrees of damage to their anal self-control function. Goligher (1962) reported 10% of air leaks, 3% of feces, and 2% of feces. Bennett (1963) and others reported that 26% of patients with mild incontinence and 9% of air leaks. 6% of stool leakage and 17% of pollution. The above-mentioned clinical statistics also confirmed that the existence of anal cushion is important for anal self-control. Therefore, some people call the anal cushion a "physiologic anal sphincter" (physiologic anal sphincter). Therefore, when designing an operation for patients with incontinence, the reconstruction of the anal cushion should be considered, that is, the artificial anal cushion should be made of compressible materials and implanted in the anal canal. In order to improve the mechanical performance of the weak sphincter, the anal canal can be kept closed when the sphincter is relaxed, and solid stools can be allowed to pass through during defecation.
Most patients with hemorrhoids have increased pressure in the anal canal. Some people have suggested that high pressure in the anal canal can affect the return of venous blood in the blood vessels to form hemorrhoids during defecation. This statement lacks anatomical and physiological basis. When the pad is congested and swelled, the sphincter is in a relaxed state rather than a contracted state; even if the vein passing through the sphincter is blocked, the blood in the anal pad can still flow back through the perforating vein on the wall of the anal canal, and blood stasis is impossible. Besides, the blood vessels in the anorectal area are very complicated. Steltzner (1963) once pointed out that the cavernous venous space in the upper anal canal (hemorrhoid area) is a normal structure. The blood in the space comes from small arteries, and its blood flow control factors are not yet understood. Therefore, the exact mechanism of high anal pressure affecting hemorrhoids is not yet satisfactory.
To sum up, the anal cushion is a special mucosal epithelium rich in arteriovenous anastomosis, a large number of Treitz muscle fibers, is a normal anatomical entity of the human body, its main function is to assist the sphincter to close the anus. The modern concept of hemorrhoids believes that changes in pelvic floor dynamics, Treitz muscle degeneration, and dysregulation of arteriovenous anastomosis in the anal cushion can lead to hypertrophy or prolapse of the anal cushion.