While in the military I worked as a radiology technologist. Working in a hospital you would be amazed of all the extreme objects people women/men shove up their ass for sexual enjoyment. I was in several cases where the rectal muscle was stretched to the point of being torn to where the sphincter would not relax and contract the patient had to use a colostomy bag until they could schedule muscle repair on their sphincter.
I was also in on a case where while using a anal probe the patient perfeated the sigmoid colon. The sigmod is the S curve from your colon to your rectum anatomically speaking. The patient had to have imediated surgery to prevent peritonitis or abdominal cavity infection from fecal bacteria.
Some of the funniest cases were the patients that would come in for a barium enema, to do a barium enema a balloon tip catheter must be inserted into the rectum and the balloon is inflated to keep the catheter from coming out and blowing barium all over the place during the exam. There are different sized balloons made for cases where patients have stretched sphincter muscle the biggest sized ballon is a #10 onion skin balloon, you would have patients where it was obvious they had frequent anal penetration and these patients would squirm and yell like they never had anything shoved up their ass many of these patients sphincter muscle could not hold back a #10 onion skin balloon so you knew that their ass had been reamed out pretty good.