You're right - it's not necessarily a surgical procedure, but it's most definitely invasive. You're having a foreign object inserted into your body while under sedation - and sedation can be just as dangerous as general anesthesia.
Besides that any cursory/basic research tells you that you will suffer nausea, heart burn, pain, vomiting, diarrhea, gastric dumping, an inability to eat solid foods for a significant length of time, bloating, cramps, etc.
Yet people come here time and time and time again saying that they've ALREADY SCHEDULED the procedure and they want to know what to expect. And my questions are:
1 - What kind of doctor schedules a procedure with these known side effects and without first informing the patient of all of them
2 - What kind of person schedules a procedure that involves sticking foreign objects into their bodies while they're under sedation w/out first researching the process?
And with regard to #2, I'm not talking about the person who comes and says that they're looking for more info, but those who say "My procedure is tomorrow and I don't know what to expect" or "I've scheduled this for next week can someone tell me what their experience has been." Those are the things you should ask BEFORE you make the decision - not after.