Buttplug Anal Capture
A Buttplug is often used for Anal stretching, since they are readily available in very large sizes and effectively designed for the purpose. Buttplugs are held in position by an indent near their base, around which the anal muscles contract. In order to keep the buttplug from being pushed too far into the intestine after insertion, a secondary lip retains it. However, if this lip is too small (either in diameter, or in terms of its sturdiness; the larger the plug, the greater the inward pull can be), or the indent groove is too small to retain it in place, the plug can be pulled inward.
This warning was received from a doctor in the Netherlands:
I would like to warn extreme anal stretchers not to insert XXL buttplug SI 40201 from SI novelties (14.5" circumference). The plug may slip inside, as happened to me, and you will need medical help to have it removed. The base of the plug is too thin and flexible and too close to the widest part of the plug. A larger plug, the Jumbo Big Boy with 15" circumference, is safer.
You can see how it happens in the photos below, which at their conclusion required an embarrassing visit to the hospital ER to have it extracted.
If you have a buttplug (or other anal stretching device) get stuck, do not push! Trying to force it out will make matters worse as it just contracts the muscles and pushes it upward. You can try relaxing and either using gravity to help it drop out or very gently pulling on it if you're able to get a grip (or if it has a retrieval strap). If it doesn't come out after a few hours or you start to experience any pain, go to the hospital emergency room.