What was that with your butt? ⇐ General

[Anonymous]

Hello everyone!
When my wife sometimes stands on all fours, her butt opens up the size of a 5 ruble coin. Approximately as in the photo (photo from the Internet).
At the same time, there are no complaints. There is no incontinence, it can close so tightly that you can’t even put a finger through it. AS occurs very rarely (about once a year).
What is it? Is it an anatomical feature or is it hiding something?
You need to register to see the link.