Why anal fissures don't cause constipation

Why doesn’t anal fissure cause constipation?

Anal fissures are not constipation because of excessive pressure behind the anal canal. If the internal sphincter contracts or spasms excessively, the anal canal posterior midline ischemia occurs, and women exert too much force during childbirth, anal fissures may also occur. Anal canal stenosis or anal sinusitis may also cause anal fissures.

1. Anatomical factors

The external anal sphincter is a ligamentous tissue behind the anus. Although it is very hard, it has poor elasticity. The levator ani muscles are mostly located on both sides of the anal canal, making the muscles in the front and back of the anal canal not as hard as the sides and easily damaged. If the pressure behind the anal canal is too high, it will cause anal fissures.

2. Internal sphincter tension

Many patients with anal fissures have excessive contraction of the internal sphincter, especially those with radiating internal sphincter spasm. Anal fissures are difficult to heal and the condition is prone to recurrence.

3. Ischemic factors

Anal fissures can also occur when there is ischemia in the posterior midline of the anal canal. This is because the capillaries in this area are sparse, so the blood flow is often insufficient.

4. Infection around the dentate line

If there is chronic inflammation near the dentate line, such as chronic anal sinusitis, the inflammation will spread to subcutaneous abscesses, and then the ulcers will develop into chronic ulcers. However, once the anal canal is damaged, it is difficult to heal, which may be caused by the damage to the anal canal and infection. When the patient is infected, the inflammatory cells in the area will release a substance called collagenase, which prevents the regeneration and recovery of the epithelial tissue, and then it is difficult to heal, and anal fissures will recur.

5. Childbirth factors

Anal fissures can also occur during certain special periods. For example, if a woman exerts too much force during childbirth, the anal canal and perineum may tear, bleed, and experience pain, leading to anal fissures.

6. Anal canal stenosis

For patients with congenital anal canal malformation, acquired traumatic surgery, or even anal canal stenosis, once the stool is dry, it can easily cause anal canal damage and lead to anal fissure.