Anal fissure: This is a common condition that can cause rectal bleeding and pain, especially after anal intercourse. The trauma from intercourse can lead to a tear in the anal mucosa, resulting in an anal fissure.

Hemorrhoids: Hemorrhoids can become irritated or thrombosed due to the trauma from anal intercourse, leading to rectal bleeding and pain.
Proctitis: Inflammation of the rectum, which can be caused by sexually transmitted infections (STIs) or other factors, can result in rectal bleeding and pain after anal intercourse.
Rectal mucosal tear: A direct injury to the rectal mucosa during anal intercourse can cause bleeding and pain.

Rectal perforation: Although less common, a perforation of the rectum is a serious condition that requires immediate medical attention. It can occur due to excessive force during anal intercourse.
STIs (e.g., gonorrhea, chlamydia, herpes simplex virus): Certain STIs can cause rectal bleeding and pain. It's crucial to consider these infections in the differential diagnosis, especially if the patient has engaged in unprotected anal intercourse.
Colon cancer: While less likely in younger individuals, rectal bleeding can be a symptom of colon cancer. This diagnosis should not be missed, especially in patients with risk factors or those over 50 years old.

Solitary rectal ulcer syndrome: This condition involves the formation of an ulcer in the rectum, often due to chronic constipation or rectal prolapse, but can also be associated with rectal bleeding and pain after anal intercourse.
Eosinophilic proctitis: A rare condition characterized by eosinophilic infiltration of the rectal mucosa, which can cause rectal bleeding and pain. It is often associated with atopic diseases or parasitic infections.