Anal sex may make a person more susceptible to bacterial infection around the anus and rectum. This is because the lining of the rectum is not as heavy as the lining of the vagina, so it is more susceptible to tears. If the anus or rectum does get torn, it does not heal as quickly. Because feces that pass through the rectum contain bacteria, any tear in the lining is at risk of getting infected. Lining tears may lead to other problems such as an anal abscess, which can make transmission of STIs and HIV more likely. This is why unprotected anal sex is often considered riskier than unprotected oral or vaginal sex.
In extreme cases, a tear in the lining can develop into a fissure (a larger tear or crack) and may extend outside of the bowel. This is called a fistula and it is a significant medical issue because it allows feces to pass outside of the bowel, and requires major surgery to repair.
Additionally, there is some suggestion that anal sex may worsen existing hemorrhoids, so you may want to carefully consider anal sex activities if you have them. Pregnancy is not a concern during anal sex (unless vaginal sex is also included on your agenda). And although you already seem aware, it is important to mention that STIs, including HIV, can be passed to or from an anal sex partner, so using condoms is always a good idea.
A woman called laissez answered this 7 years ago.
The anus was meant to excrete fecal matter and that's it. Not accept foreign objects that are too large for the diameter and are usually forced in a violent manner. Even casual anal sex very often leads to anal leakage which means the fluid that naturally develops in your bowels will begin to seep out. This is because the sphincter, or seal, that is like a muscle that controls its opening gets worn out prematurely. So basically you're accelerating the natural process and giving yourself an old woman's butt long before you are old.