Gastro thoughts on colonics

I had a gasto visit - the topic of colonics to clear out the colon came up rather then take the meds they suggest. He said he would refuse a patient a colonoscopy who just did a colonic rather then take the meds. He said the colonics do not empty the complet length of the colon. He has found about half way up the procedure colon is still full. I always do a liquid fast for about four days prior to a colonic- so I feel like im empty prior to the procedure and in most cases am. Does anyone have any experience with a colonoscopy? and Colonicss? and the medication expected prior to the procedure? He was a bit of an old school gastro guy but was open to talking about alternative health things. He has alot of experience doing colonoscopys.