What causes anal fissure?

Anal fissure is a relatively serious anorectal disease. Patients with anal fissure will experience severe pain during defecation and will also have blood in the stool. Anal fissure can be cured. There are many causes of anal fissure, including anatomical factors, such as the increased pressure of feces on the posterior part of the bile duct. It may also be caused by trauma. If constipation leads to excessive force during defecation, it can also cause this phenomenon. There are also other causes such as infection, or congenital stenosis of the bile duct, etc.

What causes anal fissure? 1. Anatomical factors:

The superficial part of the external anal sphincter forms the anococcygeal ligament behind the anus, which is relatively hard and has poor elasticity. Most of the levator ani muscles are attached to the sides of the anal canal, so the front and back of the anal canal are not as strong as the sides and are easily damaged. The anal canal and rectum form the anorectal angle, which makes the back of the anal canal bear great pressure from feces, etc., which are all factors that cause anal fissures. 2. Trauma:

Patients with chronic constipation are prone to damage the skin of the anal canal due to their dry and hard stools and excessive force when defecation. Repeated damage can cause deep lacerations that extend through the entire layer of skin, forming chronic infectious ulcers. It has been reported that constipation causes anal fissures in 14% to 24% of cases, but constipation may also be a consequence of anal fissures due to the patient's fear of defecation. In addition, birth trauma can also cause anal fissures, accounting for about 3% to 9%. Frequent bowel movements during diarrhea can easily damage the sensitive and tight anal canal, and repeated damage can lead to chronic infectious ulcers.

Chronic inflammation near the dentate line, such as anal sinusitis in the posterior median area, spreads downward to cause subcutaneous abscesses, which rupture and become chronic ulcers. The reason why the anal canal is difficult to heal after injury is still unknown. Some people believe that it is mainly caused by injury and infection. During infection, inflammatory cells can release collagenase to prevent the regeneration and extension of epithelial tissue. 4. Ischemia :

Recently, some people have proposed that ischemia of the posterior midline of the anal canal is the reason why anal fissures are common in this area, because the distal end of the anal canal is supplied by the inferior rectal artery, which passes through the ischiorectal fossa and branches out into small branches through the anal sphincter to the mucosa, but most posterior commissures lack branches of the inferior rectal artery (accounting for 85%). Capillary morphological studies also suggest that the capillaries inside the internal sphincter at the posterior midline are relatively sparse. Some people used laser Doppler blood flowmetry to measure that the blood flow at the posterior anal junction is less than that in other quadrants. All of the above indicate that ischemia is indeed the main factor in the development of chronic anal fissure.

Anal canal stenosis caused by congenital malformation, trauma or surgery is more likely to be damaged and cause anal fissures when dry stool passes.