Learn About Anal Fissures
By far the most painful of the rectal and anal disorders that we discuss are anal fissures, which are tears in the tissue that lines your anus. Although some fissures are painless and the only symptom is occasional bleeding, many can be completely debilitating.
Some fissures are like small papercuts and others are more severe, longer, deeper tears. Pain from the anal fissure is intense during a bowel movement and can last 30 minutes to a few hours following the bowel movement.
The most common causes of acute anal fissures are enlarged or hard stool, straining during a bowel movement, constipation, and diarrhea. Anal sex can also cause anal fissures but Huffington Post has a helpful article with tips for avoiding tearing during penetration.