@gwhap
You wrote: "Assisted shower, pictures on the wall and an enema before the colonic?"
The shower is a new one for me, but not the enema. From the rest of the post, the lady must have been using a closed system.
With a new client, the therapist simply can't tell how much poo is in the client or how firm it is. The simple fact is if a client has a big lump of firm or hard poo, in their butt, the water will go in and pretty soon will want to come out... urgently. But, if the poo blocks the speculum, the result will be a very big, stinky mess. It will all come out in a rush, flooding the treatment table and probably the floor too. And it won't be clear water. No therapist wants to deal with that. Ever.
Hence, the client will be asked when they last pood. If it's more than roughly 12 hours, the therapist will either suggest an initial fill, to be "taken to the toilet" or an enema. My favorite therapist routinely gives a disposable bag full of warm water, soap optional, on the treatment table before every colonic.
She says the preliminary enema makes the colonic far more effective for all her clients, and she is very good at getting the full bag into clients.
Personally, I'd never go to a male therapist.
As to sexual arousal, it's not a factor. I simply enjoy lying comfortably and being completely cleaned out. Comparing a colonic to an enema, I actually prefer the colonic. With the enema, you must hurry to the toilet or potty when it works. There is always the worry that you'll "let loose" before getting seated and the resulting mess.
With a closed system, you simply tell the therapist "release" and she turns the valve and you're pooing. In fact, there is no way you cannot poo, because the speculum holds your passage open allowing free flow of everything. As long as the valve is open, you're pooing. Period.
On an open system, you poo at will, but you must make some effort to push out the water, as with an enema release.
Finally, the bidet was certainly a nice touch. My closed system therapist has a toilet very close to her treatment table, but there is really no way of cleaning one's butt after pooing or the session. It would be a great joy to have a plumbed-in bidet right beside the toilet.