2021年10月28日星期四

What are the causes of hemorrhoids?

Factors causing hemorrhoids: downward movement of anal pad:

Hemorrhoids are the result of the downward movement of some mucosa and submucosal tissue caused by the degeneration of anal canal supporting tissue. The mucosal sliding theory was proposed for the first time. Later, parks and Thomson further developed it and put forward the "cushion theory" under anal canal mucosa. Anal cushion is composed of dilated veins, smooth muscle, collagen fibers and elastic connective tissue, It can make the anal mucosa adapt to the change of intestinal cavity size, and plays an important role in helping to close the anus and maintain the self-control of the anus. Degenerative changes of connective tissue and excessive force during defecation can make the anal pad move down and cause hemorrhoid symptoms. Once the anal pad sags, it will inevitably lead to obstruction of hemorrhoid venous reflux, congestion and edema of hemorrhoids. The degree of congestion of anal pad is not affected by anal pressure such as constipation, Besides the influence of pregnancy and other factors, it is also related to hormones, biochemical factors and emotions.

Factors causing hemorrhoids: vascular proliferation:

The submucosal tissue of the tube is very thick. Bourgery compares it to the "erectile Web", while Henrich (1980) calls it the rectal cavernous body. It is composed of a large number of blood vessels, smooth muscle, elastic fibers and connective tissue. Like a circular air cushion, it helps close the anus when the sphincter contracts. Hemorrhoids can be formed when the blood vessels in it proliferate and expand and cause abnormal hypertrophy, However, from the perspective of histomorphology, the theory of vascular proliferation is still lack of sufficient evidence.

Factors causing hemorrhoids: anal stenosis:

The theory of anal canal stenosis was put forward by brnes, mile, slack, etc. they believe that the sphincter can not be fully relaxed and promote defecation by increasing abdominal pressure, which can make hemorrhoid veins congested and internal hemorrhoids occur, and increase the shear force on the anal pad to make it move down. The theoretical basis of anal dilatation therapy is the theory of anal stenosis, although it has achieved certain clinical effects, But this theory can not explain all the problems of hemorrhoids.

Factors causing hemorrhoids: vascular disease:

It is known that venous dilatation and obstruction of venous blood reflux are the reasons for the formation of hemorrhoids. Therefore, various factors that increase venous pressure, such as increased abdominal pressure, upright position or damage to vascular wall, are related to the occurrence of hemorrhoids.

Factors causing hemorrhoids: Causes

The etiology of hemorrhoids is not completely clear and can be caused by many factors. At present, there are the following theories:

Factors causing hemorrhoids:

1. Varicose vein theory

This theory was originally put forward by Hippocrates. He noticed that hemorrhoids were filled with dilated veins, so he thought that hemorrhoids were caused by rectal and anal submucosal varicose veins. This theory was put forward first and has always been in an orthodox and important position. The theoretical basis supporting this theory is constipation and forced breath holding during defecation, often hemorrhoids and bloody stool, It has long been recognized as an important reason for the formation of hemorrhoids, because dry and hard feces and forced breath holding can cause the obstruction of hemorrhoid vein reflux and expansion. Recently, many scholars have proved that the expansion of hemorrhoid vein exists constantly from newborn infants to healthy adults, which belongs to normal tissue structure. Therefore, this theory can not explain the essence of hemorrhoids.

Factors causing hemorrhoids: 2. Increased anal pad pressure

Anal vascular pad is a kind of tissue pad located in the anal canal and rectum, referred to as "anal pad", which is an anatomical phenomenon existing after birth. The anal pad consists of three parts:

① Veins, or venous sinuses;

② Connective tissue;

③ Treitz muscle refers to the smooth muscle between the anal pad and the internal sphincter of the anal canal. It has the function of fixing the anal pad. Under normal circumstances, the anal pad loosely adheres to the muscle wall and retracts the anal canal by its own fiber contraction after defecation.

The measurement of anal pad pressure shows that the basal pressure of patients with internal hemorrhoids is significantly higher than that of the control group. The increase of basal pressure is related to the increase of vascular pad pressure. The increase of sphincter activity can lead to the increase of anal pressure and the formation of internal hemorrhoids. Sun (1990) proposed that the increase of anal resistance in patients with internal hemorrhoids is related to the congestion of hemorrhoids, but not necessarily accompanied by the increase of anal muscle tension, This view proves the correctness of the treatment method of reducing blood vessel block by injection, ligation, electrocoagulation or surgical resection, and the method of internal sphincter incision or strong anal dilation to reduce sphincter tension is worth discussing, because when the pressure in the anal pad increases, it is forced to defecate, and the sphincter is relaxed rather than contracted.

The above theories can not fully explain the occurrence of hemorrhoids, so the occurrence of hemorrhoids may be the result of the comprehensive action of many factors, or there may be multiple sources of hemorrhoids in Genesis.

Factors causing hemorrhoids: pathogenesis

Factors causing hemorrhoids: pathology

Hemorrhoids are varicose vein masses covered with mucosa protruding to the lower end of rectum and the surface of anal canal. The protruding part is also called hemorrhoid mass. Its surface is dark red or purplish red. It is closely connected with anal sphincter by spongy tissue. Its interior is curved arterioles and varicose vein plexus with thin wall. There are often thrombosis in dilated veins. Sometimes arteriovenous fistula can be found, and acute and chronic inflammation can be seen locally, The surface of internal hemorrhoids is columnar epithelium, and the surface of external hemorrhoids is squamous epithelium.

Factors causing hemorrhoids: Classification

Hemorrhoids are usually divided into three categories with the dentate line as the boundary:

(1) Internal hemorrhoids: located above the dentate line, covered with mucous membrane on the surface and formed by the expansion of internal hemorrhoid venous plexus. It is common at the left, front right and rear right of the lower rectum. At the beginning, internal hemorrhoids protrude into the intestinal cavity. Over time, they can gradually protrude outside the anus, manifested as hematochezia and prolapse. According to the clinical manifestations of internal hemorrhoids, they can be divided into non prolapsed internal hemorrhoids, external prolapsed internal hemorrhoids and Incarcerated Hemorrhoids, If the internal hemorrhoids show ring prolapse, it is also called ring hemorrhoids.

(2) External hemorrhoids: located below the dentate line, the surface is covered by skin and formed by hemorrhoid external venous plexus. It can also be divided into thrombotic external hemorrhoids, connective tissue external hemorrhoids (skin droop), varicose external hemorrhoids and inflammatory external hemorrhoids.

(3) Mixed hemorrhoids: near the dentate line, it is covered by the junction tissue of skin and mucosa. It is formed by the veins anastomosed with each other between the internal hemorrhoid vein and the external hemorrhoid venous plexus. It has two characteristics of internal hemorrhoids and external hemorrhoids.

没有评论:

发表评论