What causes severe anal fissure

Most cases of severe anal fissures are caused by failure to receive timely treatment. If anal fissure is not treated in time, bacteria will enter the body through the damaged area, affecting the tendon cells around the anus and causing ischemia. For severe anal fissures, patients should be sent to hospital for treatment in time to avoid heavy bleeding.

Anatomical factors (30%):

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.

Trauma (12%):

Patients with chronic constipation have hard and dry stools and exert excessive force when defecating, which can easily damage the skin of the anal canal. Repeated damage can cause the lacerations to penetrate deep into 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 can also be a consequence of anal fissures, caused by 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 form chronic infectious ulcers.

Infection (15%):

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.

Ischemia (10%):

Recently, some people have proposed that ischemia in the posterior midline of the anal canal is the reason why anal fissures are common in this area. This is 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 that pass through the anal sphincter to the mucosa. However, 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 in the posterior midline are relatively sparse. Some people have used laser Doppler blood flowmetry to measure that the blood flow in the posterior commissure of the anal canal is less than that in other quadrants. All of the above shows that ischemia is indeed the main factor in the onset of chronic anal fissures.