I had the chance to read through the entire thread and a few thoughts struck me. Here in the Intermountain West, enemas until clear was a common, standard bowel prep, anytime a physician or surgeon wanted a patient prepped before a procedure. That may have meant a barium enema, and in my case, a barium swallow about 50 years ago. I was given an enema prior to knee surgery and in relation to appendicitis and ultimate appendectomy as well. I know that several family members also were required to take multiple enemas for various procedures as well.
Over the years, Fleet enemas became the preferred choice. It seemed to make sense relative to the amount of nursing time and patient complaints relative to the large volume enemas. Once colonoscopies became quite routine, and replaced the barium enema and/or sigmoidoscopy, other methods of bowel prep became the preferred methods. Nowadays, laxatives, and other types of chemical solutions seem to be the only recommended methods. Interestingly, a family member needed to prep for a colonoscopy and the usual chemical solutions hadn't been effective. After consulting with the nurse, it was suggested that several large volume enemas were necessary to avoid rescheduling the colonoscopy. The enemas were administered and the procedure completed that afternoon. The prep was very adequate according to the gastroenterologist.
Having dealt with kidney stones for half of my adult life, I have undergone dozens of Cystoscopies, Lithotripsies, IVP's, Contrast CT's, and KUB's. These tests have usually been preceded by some type of bowel prep. My Urologist has always indicated that stool and gas in the bowel can obscure or hide kidney/ureter issues during the scan or x-ray. His nurse usually hands out the bowel prep with the instructions. If not, a written instruction is given and the items purchased by the patient.
In my case, and I have posted about this previously, I inquired about using enemas in lieu of the chemical methods. Because I didn't want to wait around for laxatives or chemicals to empty my bowel, usually resulting in taking time off work, enemas were taken and they were sanctioned by the doctor and his staff. While my preference was seemingly rather unusual, they adequately accomplished the intended preparation. The nurse and doctor were well aware of the "old fashioned" methods, but understood the rationale. It was all accomplished in less than an hour, and no time off was necessary. The only other request was that I take the gas relieving gels after the enemas.
It would seem pretty common to do a bowel prep prior to kidney surgery, especially if guided by x-ray or CT etc.