What Causes Constipation Post Surgery For Diverticulitis?

Hi, I had surgery a few years ago for diverticulitis , I had 12 cut off my colon after having years of attacks from that illness, everything went well and it s been 5 years now after surgery , about 6 months I started to get constipated and ended up in the hospital with eschimic bowel from constipation I had infection and a lot of bleeding for 5 days , when I came home the Dr. prescribed Polyethylene Glycol 3350 NF 527 everyday as a stool softner , my question is ...........is this safe or does it have bad side effects later on in life , like kidney promblems