I meant to ask you what fruits you were eating and having undigested pieces show up in bowel movements...I could definitely see there being problems with fruits that have tough exterior skins like apples, but bananas or even avocadoes I would think should be fairly easily digested.
With that said, I have done coffee enemas before and thought that I was getting out gall bladder stones, but upon closer examination and literally probing them and having them smoosh against the toilet bowel I realized that they were just undigested avocado pieces.
My personal opinion is that all foods need stomach acid and enzymes to digest "PROPERLY", but fruits should need less, IMO, because of the live enzymes in the fruits; according to various sources.