Anal fissures are caused mainly by trauma or injury to the lining of the anus. The most common causes include passing large or hard stools, straining during bowel movements due to constipation, and frequent diarrhea. Other causes can be childbirth, inflammatory bowel diseases like Crohn’s, anal sex, infections, and certain medical conditions that reduce blood flow or increase pressure in the anal muscles.
Common Causes
- Constipation and straining during bowel movements cause tears from hard stools or excessive pressure.
- Diarrhea irritates the area and can cause frequent stretching and tearing.
- Childbirth pressures the anal canal and can damage the delicate lining.
- Anal sex or inserting objects can overstretch and injure the lining.
- Medical conditions like Crohn’s disease, infections, and poor blood supply also increase risk.
Mechanism
The anal canal lining is thin and delicate, making it prone to tearing when stretched excessively or exposed to acidic or abrasive stools. Heavy straining and trauma cause small cracks that result in pain and bleeding, often aggravated by muscle spasms in the anal sphincter.
Hence, anal fissures mostly follow mechanical or inflammatory injury to the anal lining.
