What is more suitable for chronic constipation, colonoscopy or colonic irrigation/colon cleansing? which is more useful for eliminating constipation?

None of the above!: If you want to eliminate constipation, you should leave your colon alone and stop sticking tubes and other foreign liquids into it. You need to do 3 things which will help: eat well and drink plenty of liquids like water to stay well hyderated;. Make sure your food has enough fiber which comes from fruits, salads vegetables and grains; each meal should have these items that will give bulk to stool.