Proctalgia fugax: A condition characterized by sudden, severe rectal pain that can cause syncope due to the intense pain stimulus. This condition is relatively common and can be triggered by various factors, including anal sphincter spasms.

Anal fissure: A tear in the lining of the anus can cause severe pain, especially during bowel movements, which may lead to syncope in some cases.
Hemorrhoids: Large or thrombosed hemorrhoids can cause significant rectal pain, potentially leading to syncope, especially if the pain is sudden and severe.
Rectal abscess: An infected collection of pus in the rectum can cause severe pain, fever, and potentially lead to syncope if the infection is severe.

Rectal cancer: Although less common, rectal cancer can cause rectal pain and potentially lead to syncope, especially if there is significant bleeding or tumor burden.
Inflammatory bowel disease (IBD): Conditions like Crohn's disease or ulcerative colitis can cause severe rectal pain, bleeding, and potentially lead to syncope due to dehydration, anemia, or electrolyte imbalances.
Infectious proctitis: Infections like gonorrhea, herpes, or CMV can cause severe rectal pain, bleeding, and potentially lead to syncope, especially in immunocompromised individuals.

Solitary rectal ulcer syndrome: A rare condition characterized by a single ulcer in the rectum, which can cause rectal pain, bleeding, and potentially lead to syncope.
Rectal endometriosis: A rare condition where endometrial tissue grows in the rectum, causing cyclical rectal pain, bleeding, and potentially leading to syncope.
Ehlers-Danlos syndrome: A rare genetic disorder that can cause rectal pain, bleeding, and potentially lead to syncope due to gastrointestinal complications.