I guarantee that your guts are NOT going to fall out your butt from having anal sex.
There are a LOT of scare stories out there about anal sex. Why? Some people feel either scared of it, or feel intimidated by it, or feel jealous that other people are enjoying it. Also, there is the whole "it's immoral" group and they intentionally put out untrue things about anal sex to scare people away. They are the same people who put out horror stories about PIV sex, about GLBT sex, about.... everything they feel threatened by. These people are not to be trusted as they have an agenda: to try to convince you NOT to have sex or at least not enjoy it when you do have it.
If you want the low down on anal sex and anal play, I suggest reading
Tristan Taoromino's books on the subject. In her research she has found that hemorrhoids are actually LESS common in people who engage in healthy anal sex and healthy anal play.
Most people who have rectal prolapse
have never had anal sex but have medical problems that precipitate the issue.
I think there are enough healthy discussions on Eden alone to convince you that these horror stories are just that: horror stories meant to scare people away from this incredibly enjoyable form of sexual contact.
Of course, precautions need to be taken, you need to use a proper lube, you need to be relaxed, you need to
want to have the anal contact, you need to do some of YOUR OWN RESEARCH to know what you are doing.
I would start with listening to what people on Eden have to say and read Tristan Taoramino's books, before believing this silly scary stuff that isn't based on medical fact.