Regarding a single session, it unfortunately won't clean your whole colon if you've been constipated for a long time. As an example, imagine pushing water through a 5 foot pipe with mud packed all the way through it. It will take a few tries to move the mud through the pipe huh? So it depends how much "mud" is in your pipe!! One session hopefully will help you have a bowel movement and clean the lower portion of your colon at best. I would save up money for a few sessions. It really depends on your age and health history. Tell us about your history, how long you've not been pooping properly and if you have other symptoms. If you were compacted like me, then you'll definately need more. I actually started to move ALOT of faeces on session 3. It takes time to undo years of problems, and it is worth the money.