Not the answer you are looking for, but eat more fiber, drink more water, and try to poo about 30 minutes before you play. You can also look into an enama/douche set.

I agree with all of this. Especially the don't hurt yourself.

I use a small enema before play and it helps, but there is nothing you can do to be 100% sure.

We have three different vascular systems. Our heart/brain, our bodies frame muscles, and our gut. Our heart and brain are always preferentially provided with blood, but the muscles and gut kind of "share" circulation. It is why you cramp after eating if you swim too soon or try and do a run. More blood flow is in the gut, less in the muscles. If you force the body to divert blood to the muscles, such as running after a meal, the food will "sit" in the gut and gassy feeling/heartburn can happen. This is a simplified explanation, but bottom line, you had a meal, this started more active parastalsis in your gut (the rhythmic movement that makes food progress), so you increased the chance of stool being in the rectum. On top of that, anything in the rectum (your body does not know if it is stool or a toy), causes parastalsis as well.
So, what you had happen CAN happen and is normal. You should not eat within about four hours before doing play like this (in your case), and make sure you have had a bowel movement if you even think there is anything in the rectum.

You can always do a small enema cleanse, as many here suggested, but that can be harsh over time, on the tissues. The other thing that some porn stars do, or so I have read, is take an Imodium tablet about an hour before anal play to slow down parastaltic activity. However, I would never recommend this, as it seems extreme to take a medication you don't really need, in order to do anal play. I worry that you could throw off your normal digestion/bowel habits that way.

Just timing of food and maybe a small bit of "internal cleansing" would be enough.

It has happened to me before, i don't think it has to much to do with when you eat because i am a woman that has been constipated for years where i am lucky to go twice a week.so not sure that has anything to do with it,i always tell my fiance if anything it packs it up there more.

Stimulation of the anus and rectum tell the body it is time to expel and that brings the colon into play. The best way to avoid this is simply to eat very "low residue" meals if you know anal play is happening in the near future

link

Also, we make sure we TRY and go to the bathroom and empty our bowels a couple hours prior to anal play. After that, everything should be nice and empty.

We have never had an "accident", although we are serious into anal play...however, while we don't use enema's or other "cleaners", we know a lot of people here swear by them. (Some say just a bit of warm water works), so you might read those posts as well.

Best wishes for lots of fun.