I'm with Kid on this one. I have very longstanding IBS since at latest age 13-14. At that age they called it Spastic Colon then later decided on IBS. I haven't had a real attack in over 30 years, but every now and then it starts to feel like an episode is starting, but goes away. I think mine would now be called IBS-A, though I'm not sure. My symptoms during attacks are primarily excruciating abdominal cramps for hours at a time, but rarely associated with constipation or diarrhea.
As a result, my theory is that the presence of baseline but dormant IBS may be making my colon and especially rectum and anus much more sensitive to irritation than without IBS, but it's just a theory. My usual enema is just plain 0.9% NaCl/table salt, but sometimes I do experiment for (hopefully) enjoyment. Because of the ease of irritation, I've learned over the last year or two to experiment slowly and carefully. I mostly prefer a single large enema or maybe two in a row if my anus and rectum don't get too irritated. Normally I do 2.5-4 quarts of saline or saline plus about 1 tsp Castile liquid soap per quart if I want soap, and retain for usually 15-30 minutes. Sometimes while I'm timing retention, I'll be so comfortable and pleasantly distended that I fall asleep, and sometimes wake up having retained for over an hour, with no problems. I once last year tried glycerine at 5% in saline and had a very enjoyable time, with the advertised very gassy or grumbly belly but no real cramping. The next time, it turns out I went too high too fast and tried 10% glycerine in saline, which gave me just about intolerable cramps and evacuation urges. I'll probably try the 5% again sometime soon, but that's probably as high as I can stand for now.
I'm expecting delivery of a SiliconeNozzles colon tube in today's mail, so I'm going to probably have to learn to take a smallish first cleansing enema, maybe 1.5-2 quarts, before starting to play with inserting the CT as far as I can. I'm looking forward to the process of learning to snake the CT in most of the way, assuming my anatomy and physiology cooperate.