What is the risk of transmission from unprotected anal sex between an HIV+ "bottom" to an HIV- "top"?
It is possible to become HIV infected as the insertive (top) partner during anal sex without a condom. Unprotected insertive anal sex poses a smaller risk for transmission than unprotected receptive anal sex, but the risk is there.
HIV infected fluids coming into contact with the urethra could lead to infection. There is also evidence that uncircumcised men may be at greater risk for infection during unprotected insertive sex than circumcised men (the interior lining of the foreskin contains cells prone to infection).
The main concern for the insertive partner during anal sex is that trauma to the rectum during anal sex can lead to bleeding. Blood can be highly infectious for HIV.
During insertive anal sex, you may be at risk for sexually transmitted diseases besides HIV. There is a high incidence of STD transmission among men who have unprotected anal sex with other men.
While the risk for transmission is lowerfor the insertive partner, transmission is possible and does happen. Try not to take any chances when having anal sex, whether you're the top or bottom, and use a condom.