Proctitis is inflammation of the lining of the rectum, the lower end of the large intestine leading to the anus. Common causes of proctitis are sexually transmitted diseases (STDs), non-STD infections, anorectal trauma, ulcerative colitis and Crohn’s disease, radiation therapy, and antibiotic use.
https://my.clevelandclinic.org/health/diseases/5964-proctitis

