Yes. Any unprotected intercourse (penis to vagina, penis to anus, penis to mouth) can cause STIs. Long before, STIs have caused proctitis (inflammation of the rectum), some may extend way up into the colon. HPV, the cause of genital warts, can also be acquired from anal sex. Any skin to mucosa (thin lining of cells in mouth, anus and vagina) contact can potentially cause STIs, more so if the skin or mucosa will have superficial cuts or wounds, some of which may not be visible or felt at all. Virtually all STIs can be transmitted through anal sex. More importantly, the rectum has billions of coliform bacteria. These bacteria are very pathogenic, which means they have a very high potential to cause disease. Engaging in unprotected anal sex will facilitate entry of these bacteria into the urethra (passageway of urine) and will cause urethritis (inflamed urethra). After the inflammation, wound healing will occur and sometimes the scar formation can constrict (narrow down) the urethra making it hard and painful to pee. If the stricture (constricted area) totally obstructs the urethra, the urine will dam up and the kidneys can get damaged. Surgery may be warranted if this happens so that the obstruction can be relieved and restore flow of urine. In some unfortunate individuals, the kidney damage is too extensive and may require kidney transplant. I do hope I have answered your question. Take care always.
These Q&A’s are for educational purposes and should not be relied upon as a substitute for medical advice you may receive from your physician. If you have a medical emergency, please call 911. These answers do not constitute or initiate a patient/doctor relationship.