They do for me. I have a totally disabled wife who requires ninety percent of my time as caregiver so there's no opportunity for finding sexual relief in the normal way. I can, and do, masturbate to ejaculation on a regular basis, but for some reason masturbating while taking an enema provides a totally different satisfying sexual experience.
At first I was just using enemas to relieve constipation. It was quick and easy compared to laxatives. When I discovered that masturbating relieved the discomfort that sometimes accompanied an enema, I looked forward to the feeling of pressure that stiffened my erection and the discomfort turned into a pleasurable sensation while I masturbated. Eventually, though, internal pressure increased to the point that I had to get up and run for the toilet, often leaking on the way!
I solved the pressure and leaking problem with a butt plug. as soon as the bag is empty I replace the nozzle with the butt plug, then I relax and masturbate though two or three pressure waves. When I get up and go into the bathroom another pressure wave starts, but instead of removing the butt plug I masturbate some more standing up, usually to ejaculation, and by then the pressure wave has passed and I can sit down and remove the butt plug.